Chapter 23 MySQL NDB Cluster 8.0

Table of Contents

23.1 NDB Cluster Overview
23.1.1 NDB Cluster Core Concepts
23.1.2 NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions
23.1.3 NDB Cluster Hardware, Software, and Networking Requirements
23.1.4 What is New in NDB Cluster
23.1.5 Options, Variables, and Parameters Added, Deprecated or Removed in NDB 8.0
23.1.6 MySQL Server Using InnoDB Compared with NDB Cluster
23.1.7 Known Limitations of NDB Cluster
23.2 NDB Cluster Installation
23.2.1 Installation of NDB Cluster on Linux
23.2.2 Installing NDB Cluster on Windows
23.2.3 Initial Configuration of NDB Cluster
23.2.4 Initial Startup of NDB Cluster
23.2.5 NDB Cluster Example with Tables and Data
23.2.6 Safe Shutdown and Restart of NDB Cluster
23.2.7 Upgrading and Downgrading NDB Cluster
23.2.8 The NDB Cluster Auto-Installer (No longer supported)
23.3 Configuration of NDB Cluster
23.3.1 Quick Test Setup of NDB Cluster
23.3.2 Overview of NDB Cluster Configuration Parameters, Options, and Variables
23.3.3 NDB Cluster Configuration Files
23.3.4 Using High-Speed Interconnects with NDB Cluster
23.4 NDB Cluster Programs
23.4.1 ndbd — The NDB Cluster Data Node Daemon
23.4.2 ndbinfo_select_all — Select From ndbinfo Tables
23.4.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)
23.4.4 ndb_mgmd — The NDB Cluster Management Server Daemon
23.4.5 ndb_mgm — The NDB Cluster Management Client
23.4.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables
23.4.7 ndb_config — Extract NDB Cluster Configuration Information
23.4.8 ndb_delete_all — Delete All Rows from an NDB Table
23.4.9 ndb_desc — Describe NDB Tables
23.4.10 ndb_drop_index — Drop Index from an NDB Table
23.4.11 ndb_drop_table — Drop an NDB Table
23.4.12 ndb_error_reporter — NDB Error-Reporting Utility
23.4.13 ndb_import — Import CSV Data Into NDB
23.4.14 ndb_index_stat — NDB Index Statistics Utility
23.4.15 ndb_move_data — NDB Data Copy Utility
23.4.16 ndb_perror — Obtain NDB Error Message Information
23.4.17 ndb_print_backup_file — Print NDB Backup File Contents
23.4.18 ndb_print_file — Print NDB Disk Data File Contents
23.4.19 ndb_print_frag_file — Print NDB Fragment List File Contents
23.4.20 ndb_print_schema_file — Print NDB Schema File Contents
23.4.21 ndb_print_sys_file — Print NDB System File Contents
23.4.22 ndb_redo_log_reader — Check and Print Content of Cluster Redo Log
23.4.23 ndb_restore — Restore an NDB Cluster Backup
23.4.24 ndb_select_all — Print Rows from an NDB Table
23.4.25 ndb_select_count — Print Row Counts for NDB Tables
23.4.26 ndb_setup.py — Start browser-based Auto-Installer for NDB Cluster (DEPRECATED)
23.4.27 ndb_show_tables — Display List of NDB Tables
23.4.28 ndb_size.pl — NDBCLUSTER Size Requirement Estimator
23.4.29 ndb_top — View CPU usage information for NDB threads
23.4.30 ndb_waiter — Wait for NDB Cluster to Reach a Given Status
23.4.31 ndbxfrm — Compress, Decompress, Encrypt, and Decrypt Files Created by NDB Cluster
23.4.32 Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs
23.5 Management of NDB Cluster
23.5.1 Commands in the NDB Cluster Management Client
23.5.2 NDB Cluster Log Messages
23.5.3 Event Reports Generated in NDB Cluster
23.5.4 Summary of NDB Cluster Start Phases
23.5.5 Performing a Rolling Restart of an NDB Cluster
23.5.6 NDB Cluster Single User Mode
23.5.7 Adding NDB Cluster Data Nodes Online
23.5.8 Online Backup of NDB Cluster
23.5.9 MySQL Server Usage for NDB Cluster
23.5.10 NDB Cluster Disk Data Tables
23.5.11 Online Operations with ALTER TABLE in NDB Cluster
23.5.12 Distributed MySQL Privileges with NDB_STORED_USER
23.5.13 NDB API Statistics Counters and Variables
23.5.14 ndbinfo: The NDB Cluster Information Database
23.5.15 INFORMATION_SCHEMA Tables for NDB Cluster
23.5.16 Quick Reference: NDB Cluster SQL Statements
23.5.17 NDB Cluster Security Issues
23.6 NDB Cluster Replication
23.6.1 NDB Cluster Replication: Abbreviations and Symbols
23.6.2 General Requirements for NDB Cluster Replication
23.6.3 Known Issues in NDB Cluster Replication
23.6.4 NDB Cluster Replication Schema and Tables
23.6.5 Preparing the NDB Cluster for Replication
23.6.6 Starting NDB Cluster Replication (Single Replication Channel)
23.6.7 Using Two Replication Channels for NDB Cluster Replication
23.6.8 Implementing Failover with NDB Cluster Replication
23.6.9 NDB Cluster Backups With NDB Cluster Replication
23.6.10 NDB Cluster Replication: Bidrectional and Circular Replication
23.6.11 NDB Cluster Replication Conflict Resolution
23.7 NDB Cluster Release Notes

MySQL NDB Cluster is a high-availability, high-redundancy version of MySQL adapted for the distributed computing environment. The most recent NDB Cluster release series uses version 8 of the NDB storage engine (also known as NDBCLUSTER) to enable running several computers with MySQL servers and other software in a cluster. NDB Cluster 8.0, now available as a General Availability (GA) release beginning with version 8.0.19, incorporates version 8.0 of the NDB storage engine. NDB Cluster 7.6 and NDB Cluster 7.5, still available as GA releases, use versions 7.6 and 7.5 of NDB, respectively. Previous GA releases still available for use in production, NDB Cluster 7.4 and NDB Cluster 7.3, incorporate NDB versions 7.4 and 7.3, respectively. NDB 7.2 and older release series are no longer supported or maintained.

Support for the NDB storage engine is not included in standard MySQL Server 8.0 binaries built by Oracle. Instead, users of NDB Cluster binaries from Oracle should upgrade to the most recent binary release of NDB Cluster for supported platforms—these include RPMs that should work with most Linux distributions. NDB Cluster 8.0 users who build from source should use the sources provided for MySQL 8.0 and build with the options required to provide NDB support. (Locations where the sources can be obtained are listed later in this section.)

Important

MySQL NDB Cluster does not support InnoDB Cluster, which must be deployed using MySQL Server 8.0 with the InnoDB storage engine as well as additional applications that are not included in the NDB Cluster distribution. MySQL Server 8.0 binaries cannot be used with MySQL NDB Cluster. For more information about deploying and using InnoDB Cluster, see Using MySQL AdminAPI. Section 23.1.6, “MySQL Server Using InnoDB Compared with NDB Cluster”, discusses differences between the NDB and InnoDB storage engines.

This chapter contains information about NDB Cluster 8.0 releases through 8.0.23. NDB Cluster 8.0 is now available (beginning with NDB 8.0.19) as a General Availability release, and recommended for new deployments; the latest available release is NDB 8.0.22. NDB Cluster 7.6 and 7.5 are previous GA releases still supported in production; for information about NDB Cluster 7.6, see What is New in NDB Cluster 7.6. For similar information about NDB Cluster 7.5, see What is New in NDB Cluster 7.5. NDB Cluster 7.4 and 7.3 are previous GA releases still supported in production, although we recommend that new deployments for production use NDB Cluster 8.0; see MySQL NDB Cluster 7.3 and NDB Cluster 7.4.

Supported Platforms.  NDB Cluster is currently available and supported on a number of platforms. For exact levels of support available for on specific combinations of operating system versions, operating system distributions, and hardware platforms, please refer to https://www.mysql.com/support/supportedplatforms/cluster.html.

Availability.  NDB Cluster binary and source packages are available for supported platforms from https://dev.mysql.com/downloads/cluster/.

NDB Cluster release numbers.  NDB 8.0 follows the same release pattern as the MySQL Server 8.0 series of releases, beginning with MySQL 8.0.13 and MySQL NDB Cluster 8.0.13. In this Manual and other MySQL documentation, we identify these and later NDB Cluster releases employing a version number that begins with NDB. This version number is that of the NDBCLUSTER storage engine used in the NDB 8.0 release, and is the same as the MySQL 8.0 server version on which the NDB Cluster 8.0 release is based.

Version strings used in NDB Cluster software.  The version string displayed by the mysql client supplied with the MySQL NDB Cluster distribution uses this format:

mysql-mysql_server_version-cluster

mysql_server_version represents the version of the MySQL Server on which the NDB Cluster release is based. For all NDB Cluster 8.0 releases, this is 8.0.n, where n is the release number. Building from source using -DWITH_NDBCLUSTER or the equivalent adds the -cluster suffix to the version string. (See Section 23.2.1.4, “Building NDB Cluster from Source on Linux”, and Section 23.2.2.2, “Compiling and Installing NDB Cluster from Source on Windows”.) You can see this format used in the mysql client, as shown here:

shell> mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 8.0.23-cluster Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> SELECT VERSION()\G
*************************** 1. row ***************************
VERSION(): 8.0.23-cluster
1 row in set (0.00 sec)

The first General Availability release of NDB Cluster using MySQL 8.0 is NDB 8.0.19, using MySQL 8.0.19.

The version string displayed by other NDB Cluster programs not normally included with the MySQL 8.0 distribution uses this format:

mysql-mysql_server_version ndb-ndb_engine_version

mysql_server_version represents the version of the MySQL Server on which the NDB Cluster release is based. For all NDB Cluster 8.0 releases, this is 8.0.n, where n is the release number. ndb_engine_version is the version of the NDB storage engine used by this release of the NDB Cluster software. For all NDB 8.0 releases, this number is the same as the MySQL Server version. You can see this format used in the output of the SHOW command in the ndb_mgm client, like this:

ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @10.0.10.6  (mysql-8.0.24 ndb-8.0.23, Nodegroup: 0, *)
id=2    @10.0.10.8  (mysql-8.0.24 ndb-8.0.23, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=3    @10.0.10.2  (mysql-8.0.24 ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=4    @10.0.10.10  (mysql-8.0.24 ndb-8.0.23)
id=5 (not connected, accepting connect from any host)

Compatibility with standard MySQL 8.0 releases.  While many standard MySQL schemas and applications can work using NDB Cluster, it is also true that unmodified applications and database schemas may be slightly incompatible or have suboptimal performance when run using NDB Cluster (see Section 23.1.7, “Known Limitations of NDB Cluster”). Most of these issues can be overcome, but this also means that you are very unlikely to be able to switch an existing application datastore—that currently uses, for example, MyISAM or InnoDB—to use the NDB storage engine without allowing for the possibility of changes in schemas, queries, and applications. A mysqld compiled without NDB support (that is, built without -DWITH_NDBCLUSTER_STORAGE_ENGINE or its alias -DWITH_NDBCLUSTER) cannot function as a drop-in replacement for a mysqld that is built with it.

NDB Cluster development source trees.  NDB Cluster development trees can also be accessed from https://github.com/mysql/mysql-server.

The NDB Cluster development sources maintained at https://github.com/mysql/mysql-server are licensed under the GPL. For information about obtaining MySQL sources using Git and building them yourself, see Section 2.9.5, “Installing MySQL Using a Development Source Tree”.

Note

As with MySQL Server 8.0, NDB Cluster 8.0 releases are built using CMake.

NDB Cluster 8.0 is available beginning with NDB 8.0.19 as a General Availability release, and is recommended for new deployments. NDB Cluster 7.6 and 7.5 are previous GA releases still supported in production; for information about NDB Cluster 7.6, see What is New in NDB Cluster 7.6. For similar information about NDB Cluster 7.5, see What is New in NDB Cluster 7.5. NDB Cluster 7.4 and 7.3 are previous GA releases still supported in production, although we recommend that new deployments for production use NDB Cluster 8.0; see MySQL NDB Cluster 7.3 and NDB Cluster 7.4.

The contents of this chapter are subject to revision as NDB Cluster continues to evolve. Additional information regarding NDB Cluster can be found on the MySQL website at http://www.mysql.com/products/cluster/.

Additional Resources.  More information about NDB Cluster can be found in the following places:

23.1 NDB Cluster Overview

NDB Cluster is a technology that enables clustering of in-memory databases in a shared-nothing system. The shared-nothing architecture enables the system to work with very inexpensive hardware, and with a minimum of specific requirements for hardware or software.

NDB Cluster is designed not to have any single point of failure. In a shared-nothing system, each component is expected to have its own memory and disk, and the use of shared storage mechanisms such as network shares, network file systems, and SANs is not recommended or supported.

NDB Cluster integrates the standard MySQL server with an in-memory clustered storage engine called NDB (which stands for Network DataBase). In our documentation, the term NDB refers to the part of the setup that is specific to the storage engine, whereas MySQL NDB Cluster refers to the combination of one or more MySQL servers with the NDB storage engine.

An NDB Cluster consists of a set of computers, known as hosts, each running one or more processes. These processes, known as nodes, may include MySQL servers (for access to NDB data), data nodes (for storage of the data), one or more management servers, and possibly other specialized data access programs. The relationship of these components in an NDB Cluster is shown here:

Figure 23.1 NDB Cluster Components

In this cluster, three MySQL servers (mysqld program) are SQL nodes that provide access to four data nodes (ndbd program) that store data. The SQL nodes and data nodes are under the control of an NDB management server (ndb_mgmd program). Various clients and APIs can interact with the SQL nodes - the mysql client, the MySQL C API, PHP, Connector/J, and Connector/NET. Custom clients can also be created using the NDB API to interact with the data nodes or the NDB management server. The NDB management client (ndb_mgm program) interacts with the NDB management server.

All these programs work together to form an NDB Cluster (see Section 23.4, “NDB Cluster Programs”. When data is stored by the NDB storage engine, the tables (and table data) are stored in the data nodes. Such tables are directly accessible from all other MySQL servers (SQL nodes) in the cluster. Thus, in a payroll application storing data in a cluster, if one application updates the salary of an employee, all other MySQL servers that query this data can see this change immediately.

Although an NDB Cluster SQL node uses the mysqld server daemon, it differs in a number of critical respects from the mysqld binary supplied with the MySQL 8.0 distributions, and the two versions of mysqld are not interchangeable.

In addition, a MySQL server that is not connected to an NDB Cluster cannot use the NDB storage engine and cannot access any NDB Cluster data.

The data stored in the data nodes for NDB Cluster can be mirrored; the cluster can handle failures of individual data nodes with no other impact than that a small number of transactions are aborted due to losing the transaction state. Because transactional applications are expected to handle transaction failure, this should not be a source of problems.

Individual nodes can be stopped and restarted, and can then rejoin the system (cluster). Rolling restarts (in which all nodes are restarted in turn) are used in making configuration changes and software upgrades (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”). Rolling restarts are also used as part of the process of adding new data nodes online (see Section 23.5.7, “Adding NDB Cluster Data Nodes Online”). For more information about data nodes, how they are organized in an NDB Cluster, and how they handle and store NDB Cluster data, see Section 23.1.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”.

Backing up and restoring NDB Cluster databases can be done using the NDB-native functionality found in the NDB Cluster management client and the ndb_restore program included in the NDB Cluster distribution. For more information, see Section 23.5.8, “Online Backup of NDB Cluster”, and Section 23.4.23, “ndb_restore — Restore an NDB Cluster Backup”. You can also use the standard MySQL functionality provided for this purpose in mysqldump and the MySQL server. See Section 4.5.4, “mysqldump — A Database Backup Program”, for more information.

NDB Cluster nodes can employ different transport mechanisms for inter-node communications; TCP/IP over standard 100 Mbps or faster Ethernet hardware is used in most real-world deployments.

23.1.1 NDB Cluster Core Concepts

NDBCLUSTER (also known as NDB) is an in-memory storage engine offering high-availability and data-persistence features.

The NDBCLUSTER storage engine can be configured with a range of failover and load-balancing options, but it is easiest to start with the storage engine at the cluster level. NDB Cluster's NDB storage engine contains a complete set of data, dependent only on other data within the cluster itself.

The Cluster portion of NDB Cluster is configured independently of the MySQL servers. In an NDB Cluster, each part of the cluster is considered to be a node.

Note

In many contexts, the term node is used to indicate a computer, but when discussing NDB Cluster it means a process. It is possible to run multiple nodes on a single computer; for a computer on which one or more cluster nodes are being run we use the term cluster host.

There are three types of cluster nodes, and in a minimal NDB Cluster configuration, there are at least three nodes, one of each of these types:

  • Management node: The role of this type of node is to manage the other nodes within the NDB Cluster, performing such functions as providing configuration data, starting and stopping nodes, and running backups. Because this node type manages the configuration of the other nodes, a node of this type should be started first, before any other node. A management node is started with the command ndb_mgmd.

  • Data node: This type of node stores cluster data. There are as many data nodes as there are fragment replicas, times the number of fragments (see Section 23.1.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”). For example, with two fragment replicas, each having two fragments, you need four data nodes. One fragment replica is sufficient for data storage, but provides no redundancy; therefore, it is recommended to have two (or more) fragment replicas to provide redundancy, and thus high availability. A data node is started with the command ndbd (see Section 23.4.1, “ndbd — The NDB Cluster Data Node Daemon”) or ndbmtd (see Section 23.4.3, “ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)”).

    NDB Cluster tables are normally stored completely in memory rather than on disk (this is why we refer to NDB Cluster as an in-memory database). However, some NDB Cluster data can be stored on disk; see Section 23.5.10, “NDB Cluster Disk Data Tables”, for more information.

  • SQL node: This is a node that accesses the cluster data. In the case of NDB Cluster, an SQL node is a traditional MySQL server that uses the NDBCLUSTER storage engine. An SQL node is a mysqld process started with the --ndbcluster and --ndb-connectstring options, which are explained elsewhere in this chapter, possibly with additional MySQL server options as well.

    An SQL node is actually just a specialized type of API node, which designates any application which accesses NDB Cluster data. Another example of an API node is the ndb_restore utility that is used to restore a cluster backup. It is possible to write such applications using the NDB API. For basic information about the NDB API, see Getting Started with the NDB API.

Important

It is not realistic to expect to employ a three-node setup in a production environment. Such a configuration provides no redundancy; to benefit from NDB Cluster's high-availability features, you must use multiple data and SQL nodes. The use of multiple management nodes is also highly recommended.

For a brief introduction to the relationships between nodes, node groups, fragment replicas, and partitions in NDB Cluster, see Section 23.1.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”.

Configuration of a cluster involves configuring each individual node in the cluster and setting up individual communication links between nodes. NDB Cluster is currently designed with the intention that data nodes are homogeneous in terms of processor power, memory space, and bandwidth. In addition, to provide a single point of configuration, all configuration data for the cluster as a whole is located in one configuration file.

The management server manages the cluster configuration file and the cluster log. Each node in the cluster retrieves the configuration data from the management server, and so requires a way to determine where the management server resides. When interesting events occur in the data nodes, the nodes transfer information about these events to the management server, which then writes the information to the cluster log.

In addition, there can be any number of cluster client processes or applications. These include standard MySQL clients, NDB-specific API programs, and management clients. These are described in the next few paragraphs.

Standard MySQL clients.  NDB Cluster can be used with existing MySQL applications written in PHP, Perl, C, C++, Java, Python, Ruby, and so on. Such client applications send SQL statements to and receive responses from MySQL servers acting as NDB Cluster SQL nodes in much the same way that they interact with standalone MySQL servers.

MySQL clients using an NDB Cluster as a data source can be modified to take advantage of the ability to connect with multiple MySQL servers to achieve load balancing and failover. For example, Java clients using Connector/J 5.0.6 and later can use jdbc:mysql:loadbalance:// URLs (improved in Connector/J 5.1.7) to achieve load balancing transparently; for more information about using Connector/J with NDB Cluster, see Using Connector/J with NDB Cluster.

NDB client programs.  Client programs can be written that access NDB Cluster data directly from the NDBCLUSTER storage engine, bypassing any MySQL Servers that may be connected to the cluster, using the NDB API, a high-level C++ API. Such applications may be useful for specialized purposes where an SQL interface to the data is not needed. For more information, see The NDB API.

NDB-specific Java applications can also be written for NDB Cluster using the NDB Cluster Connector for Java. This NDB Cluster Connector includes ClusterJ, a high-level database API similar to object-relational mapping persistence frameworks such as Hibernate and JPA that connect directly to NDBCLUSTER, and so does not require access to a MySQL Server. See Java and NDB Cluster, and The ClusterJ API and Data Object Model, for more information.

NDB Cluster also supports applications written in JavaScript using Node.js. The MySQL Connector for JavaScript includes adapters for direct access to the NDB storage engine and as well as for the MySQL Server. Applications using this Connector are typically event-driven and use a domain object model similar in many ways to that employed by ClusterJ. For more information, see MySQL NoSQL Connector for JavaScript.

Management clients.  These clients connect to the management server and provide commands for starting and stopping nodes gracefully, starting and stopping message tracing (debug versions only), showing node versions and status, starting and stopping backups, and so on. An example of this type of program is the ndb_mgm management client supplied with NDB Cluster (see Section 23.4.5, “ndb_mgm — The NDB Cluster Management Client”). Such applications can be written using the MGM API, a C-language API that communicates directly with one or more NDB Cluster management servers. For more information, see The MGM API.

Oracle also makes available MySQL Cluster Manager, which provides an advanced command-line interface simplifying many complex NDB Cluster management tasks, such restarting an NDB Cluster with a large number of nodes. The MySQL Cluster Manager client also supports commands for getting and setting the values of most node configuration parameters as well as mysqld server options and variables relating to NDB Cluster. MySQL Cluster Manager 1.4.8 provides experimental support for NDB 8.0. See MySQL™ Cluster Manager 1.4.8 User Manual, for more information.

Event logs.  NDB Cluster logs events by category (startup, shutdown, errors, checkpoints, and so on), priority, and severity. A complete listing of all reportable events may be found in Section 23.5.3, “Event Reports Generated in NDB Cluster”. Event logs are of the two types listed here:

  • Cluster log: Keeps a record of all desired reportable events for the cluster as a whole.

  • Node log: A separate log which is also kept for each individual node.

Note

Under normal circumstances, it is necessary and sufficient to keep and examine only the cluster log. The node logs need be consulted only for application development and debugging purposes.

Checkpoint.  Generally speaking, when data is saved to disk, it is said that a checkpoint has been reached. More specific to NDB Cluster, a checkpoint is a point in time where all committed transactions are stored on disk. With regard to the NDB storage engine, there are two types of checkpoints which work together to ensure that a consistent view of the cluster's data is maintained. These are shown in the following list:

  • Local Checkpoint (LCP): This is a checkpoint that is specific to a single node; however, LCPs take place for all nodes in the cluster more or less concurrently. An LCP usually occurs every few minutes; the precise interval varies, and depends upon the amount of data stored by the node, the level of cluster activity, and other factors.

    NDB 8.0 supports partial LCPs, which can significantly improve performance under some conditions. See the descriptions of the EnablePartialLcp and RecoveryWork configuration parameters which enable partial LCPs and control the amount of storage they use.

  • Global Checkpoint (GCP): A GCP occurs every few seconds, when transactions for all nodes are synchronized and the redo-log is flushed to disk.

For more information about the files and directories created by local checkpoints and global checkpoints, see NDB Cluster Data Node File System Directory.

23.1.2 NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions

This section discusses the manner in which NDB Cluster divides and duplicates data for storage.

A number of concepts central to an understanding of this topic are discussed in the next few paragraphs.

Data node.  An ndbd or ndbmtd process, which stores one or more fragment replicas—that is, copies of the partitions (discussed later in this section) assigned to the node group of which the node is a member.

Each data node should be located on a separate computer. While it is also possible to host multiple data node processes on a single computer, such a configuration is not usually recommended.

It is common for the terms node and data node to be used interchangeably when referring to an ndbd or ndbmtd process; where mentioned, management nodes (ndb_mgmd processes) and SQL nodes (mysqld processes) are specified as such in this discussion.

Node group.  A node group consists of one or more nodes, and stores partitions, or sets of fragment replicas (see next item).

The number of node groups in an NDB Cluster is not directly configurable; it is a function of the number of data nodes and of the number of fragment replicas (NoOfReplicas configuration parameter), as shown here:

[# of node groups] = [# of data nodes] / NoOfReplicas

Thus, an NDB Cluster with 4 data nodes has 4 node groups if NoOfReplicas is set to 1 in the config.ini file, 2 node groups if NoOfReplicas is set to 2, and 1 node group if NoOfReplicas is set to 4. Fragment replicas are discussed later in this section; for more information about NoOfReplicas, see Section 23.3.3.6, “Defining NDB Cluster Data Nodes”.

Note

All node groups in an NDB Cluster must have the same number of data nodes.

You can add new node groups (and thus new data nodes) online, to a running NDB Cluster; see Section 23.5.7, “Adding NDB Cluster Data Nodes Online”, for more information.

Partition.  This is a portion of the data stored by the cluster. Each node is responsible for keeping at least one copy of any partitions assigned to it (that is, at least one fragment replica) available to the cluster.

The number of partitions used by default by NDB Cluster depends on the number of data nodes and the number of LDM threads in use by the data nodes, as shown here:

[# of partitions] = [# of data nodes] * [# of LDM threads]

When using data nodes running ndbmtd, the number of LDM threads is controlled by the setting for MaxNoOfExecutionThreads. When using ndbd there is a single LDM thread, which means that there are as many cluster partitions as nodes participating in the cluster. This is also the case when using ndbmtd with MaxNoOfExecutionThreads set to 3 or less. (You should be aware that the number of LDM threads increases with the value of this parameter, but not in a strictly linear fashion, and that there are additional constraints on setting it; see the description of MaxNoOfExecutionThreads for more information.)

NDB and user-defined partitioning.  NDB Cluster normally partitions NDBCLUSTER tables automatically. However, it is also possible to employ user-defined partitioning with NDBCLUSTER tables. This is subject to the following limitations:

  1. Only the KEY and LINEAR KEY partitioning schemes are supported in production with NDB tables.

  2. The maximum number of partitions that may be defined explicitly for any NDB table is 8 * [number of LDM threads] * [number of node groups], the number of node groups in an NDB Cluster being determined as discussed previously in this section. When running ndbd for data node processes, setting the number of LDM threads has no effect (since ThreadConfig applies only to ndbmtd); in such cases, this value can be treated as though it were equal to 1 for purposes of performing this calculation.

    See Section 23.4.3, “ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)”, for more information.

For more information relating to NDB Cluster and user-defined partitioning, see Section 23.1.7, “Known Limitations of NDB Cluster”, and Section 24.6.2, “Partitioning Limitations Relating to Storage Engines”.

Fragment replica.  This is a copy of a cluster partition. Each node in a node group stores a fragment replica. Also sometimes known as a partition replica. The number of fragment replicas is equal to the number of nodes per node group.

A fragment replica belongs entirely to a single node; a node can (and usually does) store several fragment replicas.

The following diagram illustrates an NDB Cluster with four data nodes running ndbd, arranged in two node groups of two nodes each; nodes 1 and 2 belong to node group 0, and nodes 3 and 4 belong to node group 1.

Note

Only data nodes are shown here; although a working NDB Cluster requires an ndb_mgmd process for cluster management and at least one SQL node to access the data stored by the cluster, these have been omitted from the figure for clarity.

Figure 23.2 NDB Cluster with Two Node Groups

Content is described in the surrounding text.

The data stored by the cluster is divided into four partitions, numbered 0, 1, 2, and 3. Each partition is stored—in multiple copies—on the same node group. Partitions are stored on alternate node groups as follows:

  • Partition 0 is stored on node group 0; a primary fragment replica (primary copy) is stored on node 1, and a backup fragment replica (backup copy of the partition) is stored on node 2.

  • Partition 1 is stored on the other node group (node group 1); this partition's primary fragment replica is on node 3, and its backup fragment replica is on node 4.

  • Partition 2 is stored on node group 0. However, the placing of its two fragment replicas is reversed from that of Partition 0; for Partition 2, the primary fragment replica is stored on node 2, and the backup on node 1.

  • Partition 3 is stored on node group 1, and the placement of its two fragment replicas are reversed from those of partition 1. That is, its primary fragment replica is located on node 4, with the backup on node 3.

What this means regarding the continued operation of an NDB Cluster is this: so long as each node group participating in the cluster has at least one node operating, the cluster has a complete copy of all data and remains viable. This is illustrated in the next diagram.

Figure 23.3 Nodes Required for a 2x2 NDB Cluster

Content is described in the surrounding text.

In this example, the cluster consists of two node groups each consisting of two data nodes. Each data node is running an instance of ndbd. Any combination of at least one node from node group 0 and at least one node from node group 1 is sufficient to keep the cluster alive. However, if both nodes from a single node group fail, the combination consisting of the remaining two nodes in the other node group is not sufficient. In this situation, the cluster has lost an entire partition and so can no longer provide access to a complete set of all NDB Cluster data.

The maximum number of node groups supported for a single NDB Cluster instance is 48.

23.1.3 NDB Cluster Hardware, Software, and Networking Requirements

One of the strengths of NDB Cluster is that it can be run on commodity hardware and has no unusual requirements in this regard, other than for large amounts of RAM, due to the fact that all live data storage is done in memory. (It is possible to reduce this requirement using Disk Data tables—see Section 23.5.10, “NDB Cluster Disk Data Tables”, for more information about these.) Naturally, multiple and faster CPUs can enhance performance. Memory requirements for other NDB Cluster processes are relatively small.

The software requirements for NDB Cluster are also modest. Host operating systems do not require any unusual modules, services, applications, or configuration to support NDB Cluster. For supported operating systems, a standard installation should be sufficient. The MySQL software requirements are simple: all that is needed is a production release of NDB Cluster. It is not strictly necessary to compile MySQL yourself merely to be able to use NDB Cluster. We assume that you are using the binaries appropriate to your platform, available from the NDB Cluster software downloads page at https://dev.mysql.com/downloads/cluster/.

For communication between nodes, NDB Cluster supports TCP/IP networking in any standard topology, and the minimum expected for each host is a standard 100 Mbps Ethernet card, plus a switch, hub, or router to provide network connectivity for the cluster as a whole. We strongly recommend that an NDB Cluster be run on its own subnet which is not shared with machines not forming part of the cluster for the following reasons:

  • Security.  Communications between NDB Cluster nodes are not encrypted or shielded in any way. The only means of protecting transmissions within an NDB Cluster is to run your NDB Cluster on a protected network. If you intend to use NDB Cluster for Web applications, the cluster should definitely reside behind your firewall and not in your network's De-Militarized Zone (DMZ) or elsewhere.

    See Section 23.5.17.1, “NDB Cluster Security and Networking Issues”, for more information.

  • Efficiency.  Setting up an NDB Cluster on a private or protected network enables the cluster to make exclusive use of bandwidth between cluster hosts. Using a separate switch for your NDB Cluster not only helps protect against unauthorized access to NDB Cluster data, it also ensures that NDB Cluster nodes are shielded from interference caused by transmissions between other computers on the network. For enhanced reliability, you can use dual switches and dual cards to remove the network as a single point of failure; many device drivers support failover for such communication links.

Network communication and latency.  NDB Cluster requires communication between data nodes and API nodes (including SQL nodes), as well as between data nodes and other data nodes, to execute queries and updates. Communication latency between these processes can directly affect the observed performance and latency of user queries. In addition, to maintain consistency and service despite the silent failure of nodes, NDB Cluster uses heartbeating and timeout mechanisms which treat an extended loss of communication from a node as node failure. This can lead to reduced redundancy. Recall that, to maintain data consistency, an NDB Cluster shuts down when the last node in a node group fails. Thus, to avoid increasing the risk of a forced shutdown, breaks in communication between nodes should be avoided wherever possible.

The failure of a data or API node results in the abort of all uncommitted transactions involving the failed node. Data node recovery requires synchronization of the failed node's data from a surviving data node, and re-establishment of disk-based redo and checkpoint logs, before the data node returns to service. This recovery can take some time, during which the Cluster operates with reduced redundancy.

Heartbeating relies on timely generation of heartbeat signals by all nodes. This may not be possible if the node is overloaded, has insufficient machine CPU due to sharing with other programs, or is experiencing delays due to swapping. If heartbeat generation is sufficiently delayed, other nodes treat the node that is slow to respond as failed.

This treatment of a slow node as a failed one may or may not be desirable in some circumstances, depending on the impact of the node's slowed operation on the rest of the cluster. When setting timeout values such as HeartbeatIntervalDbDb and HeartbeatIntervalDbApi for NDB Cluster, care must be taken care to achieve quick detection, failover, and return to service, while avoiding potentially expensive false positives.

Where communication latencies between data nodes are expected to be higher than would be expected in a LAN environment (on the order of 100 µs), timeout parameters must be increased to ensure that any allowed periods of latency periods are well within configured timeouts. Increasing timeouts in this way has a corresponding effect on the worst-case time to detect failure and therefore time to service recovery.

LAN environments can typically be configured with stable low latency, and such that they can provide redundancy with fast failover. Individual link failures can be recovered from with minimal and controlled latency visible at the TCP level (where NDB Cluster normally operates). WAN environments may offer a range of latencies, as well as redundancy with slower failover times. Individual link failures may require route changes to propagate before end-to-end connectivity is restored. At the TCP level this can appear as large latencies on individual channels. The worst-case observed TCP latency in these scenarios is related to the worst-case time for the IP layer to reroute around the failures.

23.1.4 What is New in NDB Cluster

The following sections describe changes in the implementation of NDB Cluster in MySQL NDB Cluster 8.0 through 8.0.23, as compared to earlier release series. NDB Cluster 8.0 is available as a General Availability (GA) release, beginning with NDB 8.0.19. NDB Cluster 7.6 and 7.5 are previous GA releases still supported in production; for information about NDB Cluster 7.6, see What is New in NDB Cluster 7.6. For similar information about NDB Cluster 7.5, see What is New in NDB Cluster 7.5. NDB Cluster 7.4 and 7.3 are previous GA releases still supported in production, although we recommend that new deployments for production use NDB Cluster 8.0; see MySQL NDB Cluster 7.3 and NDB Cluster 7.4.

What is New in NDB Cluster 8.0

Major changes and new features in NDB Cluster 8.0 which are likely to be of interest are shown in the following list:

  • Compatibility enhancements.  The following changes reduce longstanding nonessential differences in NDB behavior as compared to that of other MySQL storage engines:

    • Development in parallel with MySQL server.  Beginning with this release, MySQL NDB Cluster is being developed in parallel with the standard MySQL 8.0 server under a new unified release model with the following features:

      • NDB 8.0 is developed in, built from, and released with the MySQL 8.0 source code tree.

      • The numbering scheme for NDB Cluster 8.0 releases follows the scheme for MySQL 8.0, starting with version 8.0.13.

      • Building the source with NDB support appends -cluster to the version string returned by mysql -V, as shown here:

        shell≫ mysql -V
        mysql  Ver 8.0.23-cluster for Linux on x86_64 (Source distribution)
        

        NDB binaries continue to display both the MySQL Server version and the NDB engine version, like this:

        shell> ndb_mgm -V
        MySQL distrib mysql-8.0.23 ndb-8.0.23, for Linux (x86_64)
        

        In MySQL Cluster NDB 8.0, these two version numbers are always the same.

      To build the MySQL 8.0.13 (or later) source with NDB Cluster support, use the CMake option -DWITH_NDBCLUSTER.

    • Platform support notes.  NDB 8.0 makes the following changes in platform support:

      • NDBCLUSTER no longer supports 32-bit platforms. Beginning with NDB 8.0.21, the NDB build process checks the system architecture and aborts if it is not a 64-bit platform.

      • Beginning with NDB 8.0.18, it is possible to build NDB from source for 64-bit ARM CPUs. Currently, this support is source-only, and we do not provide any precompiled binaries for this platform.

    • Database and table names.  As of NDB 8.0.18, the 63-byte limit on identifiers for databases and tables is removed. These identifiers can now use up to 64 bytes, as for such objects using other MySQL storage engines. See Section 23.1.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.0”.

    • Generated names for foreign keys.  NDB (version 8.0.18 and later) now uses the pattern tbl_name_fk_N for naming internally generated foreign keys. This is similar to the pattern used by InnoDB.

  • Schema and metadata distribution and synchronization.  NDB 8.0 makes use of the MySQL data dictionary to distribute schema information to SQL nodes joining a cluster and to synchronize new schema changes between existing SQL nodes. The following list describes individual enhancements relating to this integration work:

    • Schema distribution enhancements.  The NDB schema distribution coordinator, which handles schema operations and tracks their progress, has been extended in NDB 8.0.17 to ensure that resources used during a schema operation are released at its conclusion. Previously, some of this work was done by the schema distribution client; this has been changed due to the fact that the client did not always have all needed state information, which could lead to resource leaks when the client decided to abandon the schema operation prior to completion and without informing the coordinator.

      To help fix this issue, schema operation timeout detection has been moved from the schema distribution client to the coordinator, providing the coordinator with an opportunity to clean up any resources used during the schema operation. The coordinator now checks ongoing schema operations for timeout at regular intervals, and marks participants that have not yet completed a given schema operation as failed when detecting timeout. It also provides suitable warnings whenever a schema operation timeout occurs. (It should be noted that, after such a timeout is detected, the schema operation itself continues.) Additional reporting is done by printing a list of active schema operations at regular intervals whenever one or more of these operations is ongoing.

      As an additional part of this work, a new mysqld option --ndb-schema-dist-timeout makes it possible to set the length of time to wait until a schema operation is marked as having timed out.

    • Disk data file distribution.  Beginning with NDB Cluster 8.0.14, NDB uses the MySQL data dictionary to make sure that disk data files and related constructs such as tablespaces and log file groups are correctly distributed between all connected SQL nodes.

    • Schema synchronization of tablespace objects.  When a MySQL Server connects as an SQL node to an NDB cluster, it checks its data dictionary against the information found in the NDB dictionary.

      Previously, the only NDB objects synchronized on connection of a new SQL node were databases and tables; MySQL NDB Cluster 8.0.14 and later also implement schema synchronization of disk data objects including tablespaces and log file groups. Among other benefits, this eliminates the possibility of a mismatch between the MySQL data dictionary and the NDB dictionary following a native backup and restore, in which tablespaces and log file groups were restored to the NDB dictionary, but not to the MySQL Server's data dictionary.

      It is also no longer possible to issue a CREATE TABLE statement that refers to a nonexistent tablespace. Such a statement now fails with an error.

    • Database DDL synchronization enhancements.  Work done in NDB 8.0.17 insures that synchronization of databases by newly joined (or rejoined) SQL nodes with those on existing SQL nodes now makes proper use of the data dictionary so that any database-level operations (CREATE DATABASE, ALTER DATABASE, or DROP DATABASE) that may have been misssed by this SQL node are now correctly duplicated on it when it connects (or reconnects) to the cluster.

      As part of the schema synchronization procedure performed when starting, an SQL node now compares all databases on the cluster's data nodes with those in its own data dictionary, and if any of these is found to be missing from the SQL node's data dictionary, the SQL Node installs it locally by executing a CREATE DATABASE statement. A database thus created uses the default MySQL Server database properties (such as those as determined by character_set_database and collation_database) that are in effect on this SQL node at the time the statement is executed.

    • NDB metadata change detection and synchronization.  NDB 8.0.16 implements a new mechanism for detection of updates to metadata for data objects such as tables, tablespaces, and log file groups with the MySQL data dictionary. This is done using a thread, the NDB metadata change monitor thread, which runs in the background and checks periodically for inconsistencies between the NDB dictionary and the MySQL data dictionary.

      The monitor performs metadata checks every 60 seconds by default. The polling interval can be adjusted by setting the value of the ndb_metadata_check_interval system variable; polling can be disabled altogether by setting the ndb_metadata_check system variable to OFF. A status variable (also added in NDB 8.0.16) Ndb_metadata_detected_count shows the number of times since mysqld was last started that inconsistencies have been detected.

      Beginning in version 8.0.18, NDB ensures that NDB table, log file group, and tablespace objects submitted by the metadata change monitor thread during operations following startup are automatically checked for mismatches and synchronized by the NDB binlog thread.

      NDB 8.0.18 also adds two status variables relating to automatic synchronization: Ndb_metadata_synced_count shows the number of objects synchronized automatically; Ndb_metadata_excluded_count indicates the number of objects for which synchronization has failed (prior to NDB 8.0.22, this variable was named Ndb_metadata_blacklist_size). In addition, you can see which objects have been synchronized by inspecting the cluster log.

      NDB 8.0.19 further enhances this functionality by adding databases to those objects in which changes are detected and synchronized. Only databases actually used by NDB tables are so handled; other databases which may be present in the MySQL data dictionary are ignored. This eliminates a previous requirement, for the case when a table existed in NDB but the table and the database towhich it belonged did not exist on the SQL node, to create this database manually; now in such cases, the database and all NDB tables belonging to it should be created on the SQL node automatically.

      NDB 8.0.19 also introduces the ndb_metadata_sync system variable; setting this variable to true overrides any settings that have been made for ndb_metadata_check_interval and ndb_metadata_check, causing the change monitor thread to begin coninuous metadata change detection.

      In NDB 8.0.22 and later, setting ndb_metadata_sync to true clears the list of objects for which synchronization has failed previously, which means it is no longer necessary to discover individual tables or to re-trigger synchronization by reconnecting the SQL node to the cluster. In addition, setting this variable to false clears the list of objects waiting to be retried.

      Beginning with NDB 8.0.21, more detailed information about the current state of automatic synchronization than can be obtained from log messages or status variables is provided by two new tables added to the MySQL Performance Schema. The tables are listed here:

      • ndb_sync_pending_objects: Contains information about database objects for which mismatches have been detected between the NDB dictionary and the MySQL data dictionary (and which have not been excluded from automatic synchronization).

      • ndb_sync_excluded_objects: Contains information about NDB database objects which have been excluded because they cannot be synchronized between the NDB dictionary and the MySQL data dictionary, and thus require manual intervention.

      A row in one of these tables provides the database object's parent schema, name, and type. Types of objects include schemas, tablespaces, log file groups, and tables. (If the object is a log file group or tablespace, the parent schema is NULL.) In addition, the ndb_sync_excluded_objects table shows the reason for which the object has been excluded.

      These tables are present only if NDBCLUSTER storage engine support is enabled. For more information about these tables, see Section 27.12.12, “Performance Schema NDB Cluster Tables”.

    • Changes in NDB table extra metadata.  In NDB 8.0.14 and later, the extra metadata property of an NDB table is used for storing serialized metadata from the MySQL data dictionary, rather than storing the binary representation of the table as in previous versions. (This was a .frm file, no longer used by the MySQL Server—see Chapter 14, MySQL Data Dictionary.) As part of the work to support this change, the available size of the table's extra metadata has been increased. This means that NDB tables created in NDB Cluster 8.0.14 and later are not compatible with previous NDB Cluster releases. Tables created in previous releases can be used with NDB 8.0.14 and later, but cannot be opened afterwards by an earlier version.

      This metadata is accessible using the NDB API methods getExtraMetadata() and setExtraMetadata() that were implemented in NDB 8.0.13.

      For more information, see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”.

    • On-the-fly upgrades of tables using .frm files.  A table created in NDB 7.6 and earlier contains metadata in the form of a compressed .frm file, which is no longer supported in MySQL 8.0. To facilitate online upgrades to NDB 8.0, NDB performs on-the-fly translation of this metadata and writes it into the MySQL Server's data dictionary, which enables the mysqld in NDB Cluster 8.0 to work with the table without preventing subsequent use of the table by a previous version of the NDB software.

      Important

      Once a table's structure has been modified in NDB 8.0, its metadata is stored using the data dictionary, and it can no longer be accessed by NDB 7.6 and earlier.

      This enhancement also makes it possible to restore an NDB backup made using an earlier version to a cluster running NDB 8.0 (or later).

    • Metadata consistency check error logging.  As part of work previously done in NDB 8.0, the metadata check performed as part of auto-synchronization between the representation of an NDB table in the NDB dictionary and its counterpart in the MySQL data dictionary includes the table's name, storage engine, and internal ID. Beginning with NDB 8.0.23, the range of properties checked is expanded to include properties of the following data objects:

      • Columns

      • Indexes

      • Foreign keys

      In addition, details of any mismatches in metadata properties are now written to the MySQL server error log. The formats used for the error log messages differ slightly depending on whether the discrepancy is found on the table level or on the level of a column, index, or foreign key. The format for a log error resulting from a table-level property mismatch is shown here, where property is the property name, ndb_value is the property value as stored in the NDB dictionary, and mysqld_value is the value of the property as stored in the MySQL data dictionary:

      Diff in 'property' detected, 'ndb_value' != 'mysqld_value'
      

      For mismatches in properties of columns, indexes, and foreign keys, the format is as follows, where obj_type is one of column, index, or foreign key, and obj_name is the name of the object:

      Diff in obj_type 'obj_name.property' detected, 'ndb_value' != 'mysqld_value'
      

      Metadata checks are performed during automatic synchronization of NDB tables when they are installed in the data dictionary of any mysqld acting as an SQL node in an NDB Cluster. If the mysqld is debug-compiled, checks are also made whenever a CREATE TABLE statement is executed, and whenever an NDB table is opened.

  • Synchronization of user privileges with NDB_STORED_USER.  A new mechanism for sharing and synchronizing users, roles, and privileges between SQL nodes is available beginning with NDB 8.0.18, using the NDB_STORED_USER privilege. Distributed privileges as implemented in NDB 7.6 and earlier (see Distributed Privileges Using Shared Grant Tables) are no longer supported.

    Once a user account is created on an SQL node, the user and its privileges can be stored in NDB and thus shared between all SQL nodes in the cluster by issuing a GRANT statement such as this one:

    GRANT NDB_STORED_USER ON *.* TO 'jon'@'localhost';
    

    NDB_STORED_USER always has global scope and must be granted using ON *.*. System reserved accounts such as mysql.session@localhost or mysql.infoschema@localhost cannot be assigned this privilege.

    Roles can also be shared between SQL nodes by issuing the appropriate GRANT NDB_STORED_USER statement. Assigning such a role to a user does not cause the user to be shared; the NDB_STORED_USER privilege must be granted to each user explicitly.

    A user or role having NDB_STORED_USER, along with its privileges, is shared with all SQL nodes as soon as they join a given NDB Cluster. Changes to the privileges of the user or role are synchronized immediately with all connected SQL nodes. It is possible to make such changes from any connected SQL node, but recommended practice is to do so from a designated SQL node only, since the order of execution of statements affecting privileges from different SQL nodes cannot be guaranteed to be the same on all SQL nodes.

    Implications for upgrades.  Due to changes in the MySQL server's privilege system (see Section 6.2.3, “Grant Tables”), privilege tables using the NDB storage engine do not function correctly in NDB 8.0. It is safe but not necessary to retain such privilege tables created in NDB 7.6 or earlier, but they are no longer used for access control. Beginning with NDB 8.0.16, a mysqld acting as an SQL node and detecting such tables in NDB writes a warning to the MySQL server log, and creates InnoDB shadow tables local to itself; such shadow tables are created on each MySQL server connected to the cluster. When performing an upgrade from NDB 7.6 or earlier, the privilege tables using NDB can be removed safely using ndb_drop_table once all MySQL servers acting as SQL nodes have been upgraded (see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”).

    The ndb_restore utility's --restore-privilege-tables option is deprecated but continues to be honored in NDB 8.0, and can still be used to restore distributed privilege tables present in a backup taken from a previous release of NDB Cluster to a cluster running NDB 8.0. These tables are handled as described in the preceeding paragraph.

    Shared users and grants are stored in the ndb_sql_metadata table, which in NDB 8.0.19 and later ndb_restore by default does not restore; you can specify the --include-stored-grants option to cause it to do so.

  • INFORMATION_SCHEMA changes.  The following changes are made in the display of information regarding Disk Data files in the INFORMATION_SCHEMA.FILES table:

    • Tablespaces and log file groups are no longer represented in the FILES table. (These constructs are not actually files.)

    • Each data file is now represented by a single row in the FILES table. Each undo log file is also now represented in this table by one row only. (Previously, a row was displayed for each copy of each of these files on each data node.)

    In addition, INFORMATION_SCHEMA tables are now populated with tablespace statistics for MySQL Cluster tables. (Bug #27167728)

  • Error information with ndb_perror.  The deprecated --ndb option for perror has been removed. Instead, use ndb_perror to obtain error message information from NDB error codes. (Bug #81704, Bug #81705, Bug #23523926, Bug #23523957)

  • Condition pushdown enhancements.  Previously, condition pushdown was limited to predicate terms referring to column values from the same table to which the condition was being pushed. In NDB 8.0.16, this restriction is removed such that column values from tables earlier in the query plan can also be referred to from pushed conditions. As of NDB 8.0.18, joins comparing column expressions are supported, as are comparisons between columns in the same table. Columns and column expressions to be compared must be of exactly the same type; this means they must also be of the same signedness, length, character set, precision, and scale, whenever these attributes apply.

    Pushing down larger parts of a condition allows more rows to be filtered out by the data nodes, thereby reducing the number of rows which mysqld must handle during join processing. Another benefit of these enhancements is that filtering can be performed in parallel in the LDM threads, rather than in a single mysqld process on an SQL node; this has the potential to improve query performance significantly.

    Existing rules for type compatibility between column values being compared continue to apply (see Section 8.2.1.5, “Engine Condition Pushdown Optimization”).

    These additional improvements are made in NDB 8.0.21:

    • Antijoins produced by the MySQL Optimizer through the transformation of NOT EXISTS and NOT IN queries (see Section 8.2.2.1, “Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations”) can be pushed down to the data nodes by NDB.

      This can be done when there is no unpushed condition on the table, and the query fulfills any other conditions which must be met for an outer join to be pushed down.

    • NDB attempts to identify and evaluate a non-dependent scalar subquery before trying to retrieve any rows from the table to which it is attached. When it can do so, the value obtained is used as part of a pushed condition, instead of using the subquery which provided the value.

  • Increase in maximum row size.  NDB 8.0.18 increases the maximum number of bytes that can be stored in an NDBCLUSTER table from 14000 to 30000 bytes.

    A BLOB or TEXT column continues to use 264 bytes of this total, as before.

    The maximum offset for a fixed-width column of an NDB table is 8188 bytes; this is also unchanged from releases previous to 8.0.18.

    See Section 23.1.7.5, “Limits Associated with Database Objects in NDB Cluster”, for more information.

  • ndb_mgm SHOW command and single user mode.  Beginning with NDB 8.0.17, when the cluster in single user mode, the output of the management client SHOW command indicates which API or SQL node has exclusive access while this mode is in effect.

  • Online column renames.  Beginning with NDB 8.0.18, columns of NDB tables can be renamed online, using ALGORITHM=INPLACE. See Section 23.5.11, “Online Operations with ALTER TABLE in NDB Cluster”, for more information.

  • Improved ndb_mgmd startup times.  Start times for management nodes daemon have been significantly improved in NDB 8.0.18 and later, in the following ways:

    • Due to replacing the list data structure formerly used by ndb_mgmd for handling node properties from configuration data with a hash table, overall startup times for the management server have been decreased by a factor of 6 or more.

    • In addition, in cases where data and SQL node host names not present in the management server's hosts file are used in the cluster configuration file, ndb_mgmd start times can be up to 20 times shorter than was previously the case.

  • NDB API enhancements.  Beginning with NDB 8.0.18, NdbScanFilter::cmp() and several comparison methods of NdbInterpretedCode can be used to compare table column values with each other. The affected NdbInterpretedCode methods are listed here:

    For all of the methods just listed, table column values to be compared much be of exactly matching types, including with respect to length, precision, signedness, scale, character set, and collation, as applicable.

    See the descriptions of the individual API methods for more information.

  • Offline multithreaded index builds.  It is now possible to specify a set of cores to be used for I/O threads performing offline multithreaded builds of ordered indexes, as opposed to normal I/O duties such as file I/O, compression, or decompression. Offline in this context refers to building of ordered indexes performed when the parent table is not being written to; such building takes place when an NDB cluster performs a node or system restart, or as part of restoring a cluster from backup using ndb_restore --rebuild-indexes.

    In addition, the default behaviour for offline index build work is modified to use all cores available to ndbmtd, rather limiting itself to the core reserved for the I/O thread. Doing so can improve restart and restore times and performance, availability, and the user experience.

    This enhancement is implemented as follows:

    1. The default value for BuildIndexThreads is changed from 0 to 128. This means that offline ordered index builds are now multithreaded by default.

    2. The default value for TwoPassInitialNodeRestartCopy is changed from false to true. This means that an initial node restart first copies all data from a live node to one that is starting—without creating any indexes—builds ordered indexes offline, and then again synchronizes its data with the live node, that is, synchronizing twice and building indexes offline between the two synchonizations. This causes an initial node restart to behave more like the normal restart of a node, and reduces the time required for building indexes.

    3. A new thread type (idxbld) is defined for the ThreadConfig configuration parameter, to allow locking of offline index build threads to specific CPUs.

    In addition, NDB now distinguishes the thread types that are accessible to ThreadConfig by these two criteria:

    1. Whether the thread is an execution thread. Threads of types main, ldm, recv, rep, tc, and send are execution threads; thread types io, watchdog, and idxbld are not.

    2. Whether the allocation of the thread to a given task is permanent or temporary. Currently all thread types except idxbld are permanent.

    For additonal information, see the descriptions of the indicated parameters in the Manual. (Bug #25835748, Bug #26928111)

  • logbuffers table backup process information.  When performing an NDB backup, the ndbinfo.logbuffers table now displays information regarding buffer usage by the backup process on each data node. This is implemented as rows reflecting two new log types in addition to REDO and DD-UNDO. One of these rows has the log type BACKUP-DATA, which shows the amount of data buffer used during backup to copy fragments to backup files. The other row has the log type BACKUP-LOG, which displays the amount of log buffer used during the backup to record changes made after the backup has started. One each of these log_type rows is shown in the logbuffers table for each data node in the cluster. Rows having these two log types are present in the table only while an NDB backup is currently in progress. (Bug #25822988)

  • ndbinfo.processes table on Windows.  The process ID of the monitor process used on Windows platforms by RESTART to spawn and restart a mysqld is now shown in the processes table as an angel_pid.

  • String hashing improvements.  Prior to NDB 8.0, all string hashing was based on first transforming the string into a normalized form, then MD5-hashing the resulting binary image. This could give rise to some performance problems, for the following reasons:

    • The normalized string is always space padded to its full length. For a VARCHAR, this often involved adding more spaces than there were characters in the original string.

    • The string libraries were not optimized for this space padding, which added considerable overhead in some use cases.

    • The padding semantics varied between character sets, some of which were not padded to their full length.

    • The transformed string could become quite large, even without space padding; some Unicode 9.0 collations can transform a single code point into 100 bytes or more of character data.

    • Subsequent MD5 hashing consisted mainly of padding with spaces, and was not particularly efficient, possibly causing additional performance penalties by flushing significant portions of the L1 cache.

    A collation provides its own hash function, which hashes the string directly without first creating a normalized string. In addition, for a Unicode 9.0 collation, the hash is computed without padding. NDB now takes advantage of this built-in function whenever hashing a string identified as using a Unicode 9.0 collation.

    Since, for other collations, there are existing databases which are hash partitioned on the transformed string, NDB continues to employ the previous method for hashing strings that use these, to maintain compatibility. (Bug #89590, Bug #89604, Bug #89609, Bug #27515000, Bug #27523758, Bug #27522732)

  • RESET MASTER changes.  Because the MySQL Server now executes RESET MASTER with a global read lock, the behavior of this statement when used with NDB Cluster has changed in the following two respects:

    • It is no longer guaranteed to be synonchrous; that is, it is now possible that a read coming immediately before RESET MASTER is issued may not be logged until after the binary log has been rotated.

    • It now behaves in exactly the same fashion, whether the statement is issued on the same SQL node that is writing the binary log, or on a different SQL node in the same cluster.

    Note

    SHOW BINLOG EVENTS, FLUSH LOGS, and most data definition statements continue, as they did in previous NDB versions, to operate in a synchronous fashion.

  • ndb_restore option usage.  Beginning with NDB 8.0.16, the --nodeid and --backupid options are both required when invoking ndb_restore.

  • ndb_log_bin default.  Beginning with NDB 8.0.16, the default value of the ndb_log_bin system variable has changed from TRUE to FALSE.

  • Dynamic transactional resource allocation.  Allocation of resources in the transaction corrdinator (see The DBTC Block) is now performed using dynamic memory pools. This means that resource allocation determined by data node configuration parameters such as MaxDMLOperationsPerTransaction, MaxNoOfConcurrentIndexOperations, MaxNoOfConcurrentOperations, MaxNoOfConcurrentScans, MaxNoOfConcurrentTransactions, MaxNoOfFiredTriggers, MaxNoOfLocalScans, and TransactionBufferMemory is now done in such a way that, if the load represented by each of these parameters is within the target load for all such resources, others of these resources can be limited so as not to exceed the total resources available.

    As part of this work, several new data node parameters controlling transactional resources in DBTC, listed here, have been added:

    See the descriptions of the parameters just listed for further information.

  • Backups using multiple LDMs per data node.  NDB backups can now be performed in a parallel fashion on individual data nodes using multiple local data managers (LDMs). (Previously, backups were done in parallel across data nodes, but were always serial within data node processes.) No special syntax is required for the START BACKUP command in the ndb_mgm client to enable this feature, but all data nodes must be using multiple LDMs. This means that data nodes must be running ndbmtd (ndbd is single-threaded and thus always has only one LDM) and they must be configured to use multiple LDMs before taking the backup; you can do this by choosing an appropriate setting for one of the multi-threaded data node configuration parameters MaxNoOfExecutionThreads or ThreadConfig.

    Backups using multiple LDMs create subdirectories, one per LDM, under the BACKUP/BACKUP-backup_id/ directory. ndb_restore now detects these subdirectories automatically, and if they exist, attempts to restore the backup in parallel; see Section 23.4.23.3, “Restoring from a backup taken in parallel”, for details. (Single-threaded backups are restored as in previous versions of NDB.) It is also possible to restore backups taken in parallel using an ndb_restore binary from a previous version of NDB Cluster by modifying the usual restore procedure; Section 23.4.23.3.2, “Restoring a parallel backup serially”, provides information on how to do this.

  • Binary configuration file enhancements.  Beginning with NDB 8.0.18, a new format is used for the management server's binary configuration file. Previously, a maximum of 16381 sections could appear in the cluster configuration file; now the maximum number of sections is 4G. This is intended to support larger numbers of nodes in a cluster than was possible before this change.

    Upgrades to the new format are relatively seamless, and should seldom if ever require manual intervention, as the management server continues to be able to read the old format without issue. A downgrade from NDB 8.0.18 (or later) to an older version of the NDB Cluster software requires manual removal of any binary configuration files or, alternatively, starting the older management server binary with the --initial option.

    For more information, see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”.

  • Increased number of data nodes.  NDB 8.0.18 increases the maximum number of data nodes supported per cluster to 144 (previously, this was 48). Data nodes can now use node IDs in the range 1 to 144, inclusive.

    Previously, the recommended node IDs for management nodes were 49 and 50. These are still supported for management nodes, but using them as such limits the maximum number of data nodes to 142; for this reason, it is now recommended that node IDs 145 and 146 are used for management nodes.

    As part of this work, the format used for the data node sysfile has been updated to version 2. This file records information such as the last global checkpoint index, restart status, and node group membership of each node (see NDB Cluster Data Node File System Directory).

  • RedoOverCommitCounter and RedoOverCommitLimit changes.  Due to ambiguities in the semantics for setting them to 0, the minimum value for each of the data node configuration parameters RedoOverCommitCounter and RedoOverCommitLimit has been increased to 1, beginning with NDB 8.0.19.

  • ndb_autoincrement_prefetch_sz changes.  In NDB 8.0.19, the default value of the ndb_autoincrement_prefetch_sz server system variable is increased to 512.

  • Changes in parameter maxmimums and defaults.  NDB 8.0.19 makes the following changes in configuration parameter maximum and default values:

  • Disk Data checkpointing improvements.  NDB Cluster 8.0.19 provides a number of new enhancements which help to reduce the latency of checkpoints of Disk Data tables and tablespaces when using non-volatile memory devices such as solid-state drives and the NVMe specification for such devices. These improvements include those in the following list:

    • Avoiding bursts of checkpoint disk writes

    • Speeding up checkpoints for disk data tablespaces when the redo log or the undo log becomes full

    • Balancing checkpoints to disk and in-memory checkpoints against one other, when necessary

    • Protecting disk devices from overload to help ensure low latency under high loads

    As part of this work, NDB 8.0.19 introduces two new data node configuration parameters. MaxDiskDataLatency places a ceiling on the degree of latency permitted for disk access and causes transactions taking longer than this length of time to be aborted. DiskDataUsingSameDisk makes it possible to take advantage of housing Disk Data tablespaces on separate disks by increasing the rate at which checkpoints of such tablespaces can be performed.

    In addition, three new tables in the ndbinfo database, also added in NDB 8.0.19 and listed here, provide information about Disk Data performance:

    • The diskstat table reports on writes to Disk Data tablespaces during the past second

    • The diskstats_1sec table reports on writes to Disk Data tablespaces for each of the last 20 seconds

    • The pgman_time_track_stats table reports on the latency of disk operations relating to Disk Data tablespaces

  • Memory allocation and TransactionMemory.  NDB 8.0.19 introduces a new TransactionMemory parameter which simplifies allocation of data node memory for transactions as part of the work done to pool transactional and Local Data Manager (LDM) memory. This parameter is intended to replace several older transactional memory parameters which have been deprecated.

    Transaction memory can now be set in any of the three ways listed here:

    • Several configuration parameters are incompatible with TransactionMemory. If any of these are set, TransactionMemory cannot be set (see Parameters incompatible with TransactionMemory), and the data node's transaction memory is determined as it was previous to NDB 8.0.19.

      Note

      Attempting to set TransactionMemory and any of these parameters concurrently in the config.ini file prevents the management server from starting.

    • If TransactionMemory is set, this value is used for determining transaction memory. TransactionMemory cannot be set if any of the incompatible parameters mentioned in the previous item have also been set.

    • If none of the incompatible parameters are set and TransactionMemory is also not set, transaction memory is set by NDB.

    For more information, see the description of TransactionMemory, as well as Section 23.3.3.13, “Data Node Memory Management”.

  • Support for additional fragment replicas.  NDB 8.0.19 increases the maximum number of fragment replicas supported in production from two to four. (Previously, it was possible to set NoOfReplicas to 3 or 4, but this was not officially supported or verified in testing.)

  • Restoring by slices.  Beginning with NDB 8.0.20, it is possible to divide a backup into roughly equal portions (slices) and to restore these slices in parallel using two new options implemented for ndb_restore:

    • --num-slices determines the number of slices into which the backup should be divided.

    • --slice-id provides the ID of the slice to be restored by the current instance of ndb_restore.

    This makes it possible to employ multiple instances of ndb_restore to restore subsets of the backup in parallel, potentially reducing the amount of time required to perform the restore operation.

    For more information, see the description of the ndb_restore --num-slices option.

  • Read from any fragment replica enabled.  Beginning with NDB 8.0.19, read from any fragment replica is enabled by default for all NDB tables. This means that the default value for the ndb_read_backup system variable is now ON, and that the value of the NDB_TABLE comment option READ_BACKUP is 1 when creating a new NDB table. Enabling read from any fragment replica significantly improves performance for reads from NDB tables, with minimal impact on writes.

    For more information, see the description of the ndb_read_backup system variable, and Section 13.1.20.11, “Setting NDB_TABLE Options”.

  • ndb_blob_tool enhancements.  Beginning with NDB 8.0.20, the ndb_blob_tool utility can detect missing blob parts for which inline parts exist and replace these with placeholder blob parts (consisting of space characters) of the correct length. To check whether there are missing blob parts, use the --check-missing option with this program. To replace any missing blob parts with placeholders, use the --add-missing option.

    For more information, see Section 23.4.6, “ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables”.

  • ndbinfo versioning.  NDB 8.0.20 and later supports versioning for ndbinfo tables, and maintains the current definitions for its tables internally. At startup, NDB compares its supported ndbinfo version with the version stored in the data dictionary. If the versions differ, NDB drops any old ndbinfo tables and recreates them using the current definitions.

  • Support for Fedora Linux.  Beginning with NDB 8.0.20, Fedora Linux is a supported platform for NDB Cluster Community releases and can be installed using the RPMs supplied for this purpose by Oracle. These can be obtained from the NDB Cluster downloads page.

  • NDB programs—NDBT dependency removal.  The dependency of a number of NDB utility programs on the NDBT library has been removed. This library is used internally for development, and is not required for normal use; its inclusion in these programs could lead to unwanted issues when testing.

    Affected programs are listed here, along with the NDB versions in which the dependency was removed:

    The principal effect of this change for users is that these programs no longer print NDBT_ProgramExit - status following completion of a run. Applications that depend upon such behavior should be updated to reflect the change when upgrading to the indicated versions.

  • Pushdown of outer joins and semijoins.  Work done in NDB 8.0.20 allows many outer joins and semijoins, and not only those using a primary key or unique key lookup, to be pushed down to the data nodes (see Section 8.2.1.5, “Engine Condition Pushdown Optimization”).

    Outer joins using scans which can now be pushed include those which meet the following conditions:

    • There are no unpushed conditions on the table

    • There are no unpushed conditions on other tables in the same join nest, or in upper join nests on which it depends

    • All other tables in the same join nest, or in upper join nests on which it depends, are also pushed

    A semijoin that uses an index scan can now be pushed if it meets the the conditions just noted for a pushed outer join, and it uses the firstMatch strategy (see Section 8.2.2.1, “Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations”).

    When a join cannot be pushed, EXPLAIN should provide the reason or reasons.

  • Foreign keys and lettercasing.  NDB stores the names of foreign keys using the case with which they were defined. Formerly, when the value of the lower_case_table_names system variable was set to 0, it performed case-sensitive comparisons of foreign key names as used in SELECT and other SQL statements with the names as stored. Beginning with NDB 8.0.20, such comparisons are now always performed in a case-insensitive fashion, regardless of the value of lower_case_table_names.

  • Multiple transporters.  NDB 8.0.20 introduces support for multiple transporters to handle node-to-node communication between pairs of data nodes. This facilitates higher rates of update operations for each node group in the cluster, and helps avoid constraints imposed by system or other limitations on inter-node communications using a single socket.

    By default, NDB now uses a number of transporters based on the number of local data management (LDM) threads or the number of transaction coordinator (TC) threads, whichever is greater. By default, the number of transporters is equal to half of this number. While the default should perform well for most workloads, it is possible to adjust the number of transporters employed by each node group by setting the NodeGroupTransporters data node configuration parameter (also introduced in NDB 8.0.20), up a maximum of the greater of the number of LDM threads or the number of TC threads. Setting it to 0 causes the number of transporters to be the same as the number of LDM threads.

  • ndb_restore: primary key schema changes.  NDB 8.0.21 (and later) supports different primary key definitions for source and target tables when restoring an NDB native backup with ndb_restore when it is run with the --allow-pk-changes option. Both increasing and decreasing the number of columns making up the original primary key are supported.

    When the primary key is extended with an additional column or columns, any columns added must be defined as NOT NULL, and no values in any such columns may be changed during the time that the backup is being taken. Because some applications set all column values in a row when updating it, whether or not all values are actually changed, this can cause a restore operation to fail even if no values in the column to be added to the primary key have changed. You can override this behavior using the --ignore-extended-pk-updates option also added in NDB 8.0.21; in this case, you must ensure that no such values are changed.

    A column can be removed from the table's primary key whether or not this column remains part of the table.

    For more information, see the description of the --allow-pk-changes option for ndb_restore.

  • Merging backups with ndb_restore.  In some cases, it may be desirable to consolidate data originally stored in different instances of NDB Cluster (all using the same schema) into a single target NDB Cluster. This is now supported when using backups created in the ndb_mgm client (see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”) and restoring them with ndb_restore, using the --remap-column option added in NDB 8.0.21 along with --restore-data (and possibly additional compatible options as needed or desired). --remap-column can be employed to handle cases in which primary and unique key values are overlapping between source clusters, and it is necessary that they do not overlap in the target cluster, as well as to preserve other relationships between tables such as foreign keys.

    --remap-column takes as its argument a string having the format db.tbl.col:fn:args, where db, tbl, and col are, respectively, the names of the database, table, and column, fn is the name of a remapping function, and args is one or more arguments to fn. There is no default value. Only offset is supported as the function name, with args as the integer offset to be applied to the value of the column when inserting it into the target table from the backup. This column must be one of INT or BIGINT; the allowed range of the offset value is the same as the signed version of that type (this allows the offset to be negative if desired).

    The new option can be used multiple times in the same invocation of ndb_restore, so that you can remap to new values multiple columns of the same table, different tables, or both. The offset value does not have to be the same for all instances of the option.

    In addition, two new options are provided for ndb_desc, also beginning in NDB 8.0.21:

    • --auto-inc (short form -a): Includes the the next auto-increment value in the output, if the table has an AUTO_INCREMENT column.

    • --context (short form -x): Provides extra information about the table, including the schema, database name, table name, and internal ID.

    For more information and examples, see the description of the --remap-column option.

  • Send thread improvements.  As of NDB 8.0.20, each send thread now handles sends to a subset of transporters, and each block thread now assists only one send thread, resulting in more send threads, and thus better performance and data node scalability.

  • Adaptive spin control using SpinMethod.  NDB 8.0.20 introduces a simple interface for setting up adaptive CPU spin on platforms supporting it, using the SpinMethod data node parameter. This parameter has four settings, one each for static spinning, cost-based adaptive spinning, latency-optimized adaptive spinning, and adaptive spinning optimized for database machines on which each thread has its own CPU. Each of these settings causes the data node to use a set of predetermined values for one or more spin parameters which enable adaptive spinning, set spin timing, and set spin overhead, as appropriate to a given scenario, thus obviating the need to set these directly for common use cases.

    For fine-tuning spin behavior, it is also possible to set these and additional spin parameters directly, using the existing SchedulerSpinTimer data node configuration parameter as well as the following DUMP commands in the ndb_mgm client:

    NDB 8.0.20 also adds a new TCP configuration parameter TcpSpinTime which sets the time to spin for a given TCP connection.

    The ndb_top tool is also enhanced to provide spin time information per thread.

    For additional information, see the description of the SpinMethod parameter, the listed DUMP commands, and Section 23.4.29, “ndb_top — View CPU usage information for NDB threads”.

  • Disk Data and cluster restarts.  Beginning with NDB 8.0.21, an initial restart of the cluster forces the removal of all Disk Data objects such as tablespaces and log file groups, including any data files and undo log files associated with these objects.

    See Section 23.5.10, “NDB Cluster Disk Data Tables”, for more information.

  • Disk Data extent allocation.  Beginning with NDB 8.0.20, allocation of extents in data files is done in a round-robin fashion among all data files used by a given tablespace. This is expected to improve distribution of data in cases where multiple storage devices are used for Disk Data storage.

    For more information, see Section 23.5.10.1, “NDB Cluster Disk Data Objects”.

  • --ndb-log-fail-terminate option.  Beginning with NDB 8.0.21, you can cause the SQL node to terminate whenever it is unable to log all row events fully. This can be done by starting mysqld with the --ndb-log-fail-terminate option.

  • AllowUnresolvedHostNames parameter.  By default, a management node refuses to start when it cannot resolve a host name present in the global configuration file, which can be problematic in some environments such as Kubernetes. Beginning with NDB 8.0.22, it is possible to override this behavior by setting AllowUnresolvedHostNames to true in the [tcp default] section of the cluster global confugration file (config.ini file). Doing so causes such errors to be treated as warnings instead, and to permit ndb_mgmd to continue starting

  • Blob write performance enhancements.  NDB 8.0.22 implements a number of improvements which allow more efficient batching when modifying multiple blob columns in the same row, or when modifying multiple rows containing blob columns in the same statement, by reducing the number of round trips required between an SQL or other API node and the data nodes when applying these modifications. The performance of many INSERT, UPDATE, and DELETE statements can thus be improved. Examples of such statements are listed here, where table is an NDB table containing one or more Blob columns:

    • INSERT INTO table VALUES ROW(1, blob_value1, blob_value2, ...), that is, insertion of a row containing one or more Blob columns

    • INSERT INTO table VALUES ROW(1, blob_value1), ROW(2, blob_value2), ROW(3, blob_value3), ..., that is, insertion of multiple rows containing one or more Blob columns

    • UPDATE table SET blob_column1 = blob_value1, blob_column2 = blob_value2, ...

    • UPDATE table SET blob_column = blob_value WHERE primary_key_column in (value_list), where the primary key column is not a Blob type

    • DELETE FROM table WHERE primary_key_column = value, where the primary key column is not a Blob type

    • DELETE FROM table WHERE primary_key_column IN (value_list), where the primary key column is not a Blob type

    Other SQL statements may benefit from these improvements as well. These include LOAD DATA INFILE and CREATE TABLE ... SELECT .... In addition, ALTER TABLE table ENGINE = NDB, where table uses a storage engine other than NDB prior to execution of the statement, may also execute more efficiently.

    This enhancement applies to statements affecting columns of MySQL type BLOB, MEDIUMBLOB, LONGBLOB, TEXT, MEDIUMTEXT, and LONGTEXT. Statements which update TINYBLOB or TINYTEXT columns (or both types) only are not affected by this work, and no changes in their performance should be expected.

    The performance of some SQL statements is not noticeably improved by this enhancement, due to the fact that they require scans of table Blob columns, which breaks up batching. Such statements include those of the types listed here:

    • SELECT FROM table [WHERE key_column IN (blob_value_list)], where rows are selected by matching on a primary key or unique key column which uses a Blob type

    • UPDATE table SET blob_column = blob_value WHERE condition, using a condition which does not depend on a unique value

    • DELETE FROM table WHERE condition to delete rows containing one or more Blob columns, using a condition which does not depend on a unique value

    • A copying ALTER TABLE statement on a table which already used the NDB storage engine prior to executing the statement, and whose rows contain one or more Blob columns before or after the statement is executed (or both)

    To take advantage of this improvement to its fullest extent, you may wish to increase the values used for the --ndb-batch-size and --ndb-blob-write-batch-bytes options for mysqld, to minimize the number of round trips required to modify Blobs. For replication, it is also recommended that you enable the slave_allow_batching system variable, which minimizes the number of round trips required by the replica cluster to apply epoch transactions.

  • Node.js update.  Beginning with with NDB 8.0.22, the NDB adapter for Node.js is built using version 12.18.3, and only that version (or a later version of Node.js) is now supported.

  • Encrypted backups.  NDB 8.0.22 adds support for backup files encrypted using AES-256-CBC; this is intended to protect against recovery of data from backups that have been accessed by unathorized parties. When encrypted, backup data is protected by a user-supplied password. The password can be any string consisting of up to 256 characters from the range of printable ASCII characters other than !, ', ", $, %, \, and ^. Retention of the password used to encrypt any given NDB Cluster backup must be performed by the user or application; NDB does not save the password. The password can be empty, although this is not recommended.

    When taking an NDB Cluster backup, you can encrypt it by using ENCRYPT PASSWORD=password with the management client START BACKUP command. Users of the MGM API can also initiate an encrypted backup by calling ndb_mgm_start_backup4().

    To restore from an encrypted backup, use ndb_restore with the options --decrypt and --backup-password. Both options are required, along with any others that would be needed to restore the same backup if it were not encrypted. ndb_print_backup_file and ndbxfrm can also read encrypted files using, respectively, -P password and --decrypt-password=password.

    In all cases in which a password is supplied for encryption or decryption, it must be quoted; you can use either single or double quotation marks to delimit the password.

    You can encrypt existing backup files using the ndbxfrm utility which is added to the NDB Cluster distribution in the 8.0.22 release; this program can also be employed for decrypting encrypted backup files. In addition, ndbxfrm can compress backup files and decompress compressed backup files using the same method that is employed by NDB Cluster for creating backups when the CompressedBackup configuration parameter is set to 1.

    This feature also implements the ability to enforce encrypted backups by setting RequireEncryptedBackup=1 in the [ndbd default] section of the cluster global configuration file. When this is done, the ndb_mgm client rejects any attempt to perform a backup that is not encrypted.

  • IPv6 support.  Beginning with NDB 8.0.22, IPv6 addressing is supported for connections to management and data nodes; this includes connections between management and data nodes with SQL nodes. When configuring a cluster, you can use numeric IPv6 addresses, host names which resolve to IPv6 addresses or both.

    For IPv6 addressing to work, the operating platform and network on which the cluster is deployed must support IPv6. As when using IPv4 addressing, hostname resolution to IPv6 addresses must be provided by the operating platform.

    IPv4 addressing continues to be supported by NDB. Using IPv4 and IPv6 addresses concurrently is not recommended, but can be made to work in the following cases:

    • When the management node is configured with IPv6 and data nodes are configured with IPv4 addresses in the config.ini file: This works if --bind-address is not used with mgmd, and data nodes are started with --ndb-connectstring set to the IPv4 address of the management nodes.

    • When the management node is configured with IPv4 and data nodes are configured with IPv6 addresses in config.ini: Similarly to the other case, this works if --bind-address is not passed to mgmd and data nodes are started with --ndb-connectstring set to the IPv6 address of the management node.

    These cases work because ndb_mgmd does not bind to any IP address by default.

    To perform an upgrade from a version of NDB that does not support IPv6 addressing to one that does, provided that the network supports IPv4 and IPv6, first perform the software upgrade; after this has been done, you can update IPv4 addresses used in the config.ini file with IPv6 addresses. After this, to cause the configuration changes to take effect and to make the cluster start using the IPv6 addresses, it is necessary to perform a system restart of the cluster.

  • Auto-Installer deprecation and removal.  The MySQL NDB Cluster Auto-Installer web-based installation tool (ndb_setup.py) is deprecated in NDB 8.0.22, and is removed in NDB 8.0.23 and later. It is no longer supported.

  • ndbmemcache deprecation and removal.  ndbmemcache is no longer supported. ndbmemcache was deprecated in NDB 8.0.22, and removed in NDB 8.0.23.

  • ndbinfo backup_id table.  NDB 8.0.24 adds a backup_id table to the ndbinfo information database. This is intended to serve as a replacement for obtaining this information by using ndb_select_all to dump the contents of the internal SYSTAB_0 tyable, which is error-prone and takes an excessively long time to perform.

    This table has a single column and row containing the ID of the most recent backup of the cluster taken using the START BACKUP management client command. In the event that no backup of this cluster can be found, the table contains a single row whose column value is 0.

  • Table partitioning enhancements.  NDB 8.0.23 introduces a new method for handling table partitions and fragments, which can determine the number of local data managers (LDMs) for a given data node independently of the number of redo log parts. This means that the number of LDMs can now be highly variable. NDB can employ this method when the ClassicFragmentation data node configuration parameter, also implemented in NDB 8.0.23, is set to false; when this is the case, the number of LDMs is no longer used to determine how many partitions to create for a table per data node, and the value of the PartitionsPerNode parameter (also introduced in NDB 8.0.23) determines this number instead, which is also used for calculating the number of fragments used for a table.

    When ClassicFragmentation has its default value true, then the traditional method of using the number of LDMs is used to determine the number of fragments that a table should have.

    For more information, see the descriptions of the new parameters referenced previously, in Multi-Threading Configuration Parameters (ndbmtd).

  • Terminology updates.  To align with work begun in MySQL 8.0.21 and NDB 8.0.21, NDB 8.0.23 implements a number of changes in terminology, listed here:

  • ThreadConfig enhancements.  As of NDB 8.0.23, the configurability of the ThreadConfig parameter has been extended with two new thread types, listed here:

    • query: A query threads works within a local data manager (LDM) to query fragments. A query thread also acts as a recovery thread. The number of query threads must be 0, 1, 2, or 3 times the number of LDM threads. 0 (the default, unless using ThreadConfig, or AutomaticThreadConfig is enabled) causes LDMs to behave as they did prior to NDB 8.0.23.

    • recover: A recovery thread retrieves data from a local checkpoint. A recovery thread specified as such never acts as a query thread.

    It is also possible to combine the existing main and rep threads in either of two ways:

    • Into a single thread by setting either one of these arguments to 0. When this is done, the resulting combined thread is shown with the name main_rep in the ndbinfo.threads table.

    • Together with the recv thread by setting both ldm and tc to 0, and setting recv to 1. In this case, the combined thread is named main_rep_recv.

    In addition, the maximum numbers of a number of existing thread types have been increased. The new maximums, including those for query threads and recovery threads, are listed here:

    • LDM: 332

    • Query: 332

    • Recovery: 332

    • TC: 128

    • Receive: 64

    • Send: 64

    • Main: 2

    Maximums for other thread types remain unchanged.

    For more information, see the descriptions of the ThreadConfig parameter and the ndbinfo.threads table.

    Also, as the result of work done relating to this task, NDB now employs mutexes to protect job buffers when using more than 32 block threads. While this can cause a slight decrease in performance (1 to 2 percent in most cases), it also significantly reduces the amount of memory required by very large configurations. For example, a setup with 64 threads which used 2 GB of job buffer memory prior to NDB 8.0.23 should require only about 1 GB instead in NDB 8.0.23 and later. In our testing this has resulted in an overall improvement on the order of 5 percent in the execution of very complex queries.

  • ndbmtd Thread Auto-Configuration.  Beginning with NDB 8.0.23, it is possible to employ automatic configuration of threads for multi-threaded data nodes using the ndbmtd configuration parameter AutomaticThreadConfig. When this parameter is set to 1, NDB sets up thread assignments automatically, based on the number of processors available to applications, for all thread supported thread types, including the new query and recover thread types described in the previous item. If the system does not limit the number of processors, you can do so if desired by setting NumCPUs (also added in NDB 8.0.23). Otherwise, automatic thread configuration accommodates up to 1024 CPUs.

    Automatic thread configuration occurs regardless of any values set for ThreadConfig or MaxNoOfExecutionThreads in config.ini; this means that it is not necessary to set either of these parameters.

    In addition, NDB 8.0.23 implements a number of new ndbinfo information database tables providing information about hardware and CPU availability, as well as CPU usage by NDB data nodes. These tables are listed here:

    Some of these tables are not available on every platform supported by NDB Cluster; see the individual descriptions of them for more information.

  • Hierachical views of NDB database objects.  The dict_obj_tree table, added to the ndbinfo information database in NDB 8.0.24, can provide hierarchical and tree-like views of many NDB database objects, including the following:

    • Tables and associated indexes

    • Tablespaces and associated data files

    • Logfile groups and associated undo log files

    For more information and examples, see Section 23.5.14.22, “The ndbinfo dict_obj_tree Table”.

MySQL Cluster Manager 1.4.8 also provides experimental support for NDB Cluster 8.0. MySQL Cluster Manager has an advanced command-line interface that can simplify many complex NDB Cluster management tasks. See MySQL™ Cluster Manager 1.4.8 User Manual, for more information.

23.1.5 Options, Variables, and Parameters Added, Deprecated or Removed in NDB 8.0

The next few sections contain information about NDB node configuration parameters and NDB-specific mysqld options and variables that have been added to, deprecated in, or removed from NDB 8.0.

Node Configuration Parameters Introduced in NDB 8.0

The following node configuration parameters have been added in NDB 8.0.

  • AllowUnresolvedHostNames: When false (default), failure by management node to resolve host name results in fatal error; when true, unresolved host names are reported as warnings only. Added in NDB 8.0.22.

  • AutomaticThreadConfig: Use automatic thread configuration; overrides any settings for ThreadConfig and MaxNoOfExecutionThreads. Added in NDB 8.0.23.

  • ClassicFragmentation: When true, use traditional table fragmentation; set false to enable flexible distribution of table fragments among LDMs. Added in NDB 8.0.23.

  • DiskDataUsingSameDisk: Set to false if Disk Data tablespaces are located on separate physical disks. Added in NDB 8.0.19.

  • MaxDiskDataLatency: Maximum allowed mean latency of disk access (ms) before starting to abort transactions. Added in NDB 8.0.19.

  • NodeGroupTransporters: Number of transporters to use between nodes in same node group. Added in NDB 8.0.20.

  • NumCPUs: Specify number of CPUs to use with AutomaticThreadConfig. Added in NDB 8.0.23.

  • PartitionsPerNode: Determines the number of table partitions created on each data node; not used if ClassicFragmentation is enabled. Added in NDB 8.0.23.

  • RequireEncryptedBackup: Whether backups must be encrypted (1 = encryption required, otherwise 0). Added in NDB 8.0.22.

  • ReservedConcurrentIndexOperations: Number of simultaneous index operations having dedicated resources on one data node. Added in NDB 8.0.16.

  • ReservedConcurrentOperations: Number of simultaneous operations having dedicated resources in transaction coordinators on one data node. Added in NDB 8.0.16.

  • ReservedConcurrentScans: Number of simultaneous scans having dedicated resources on one data node. Added in NDB 8.0.16.

  • ReservedConcurrentTransactions: Number of simultaneous transactions having dedicated resources on one data node. Added in NDB 8.0.16.

  • ReservedFiredTriggers: Number of triggers having dedicated resources on one data node. Added in NDB 8.0.16.

  • ReservedLocalScans: Number of simultaneous fragment scans having dedicated resources on one data node. Added in NDB 8.0.16.

  • ReservedTransactionBufferMemory: Dynamic buffer space (in bytes) for key and attribute data allocated to each data node. Added in NDB 8.0.16.

  • SpinMethod: Determines spin method used by data node; see documentation for details. Added in NDB 8.0.20.

  • TcpSpinTime: Time to spin before going to sleep when receiving. Added in NDB 8.0.20.

  • TransactionMemory: Memory allocated for transactions on each data node. Added in NDB 8.0.19.

Node Configuration Parameters Deprecated in NDB 8.0

The following node configuration parameters have been deprecated in NDB 8.0.

  • BatchSizePerLocalScan: Used to calculate number of lock records for scan with hold lock. Deprecated as of NDB 8.0.19.

  • MaxNoOfConcurrentIndexOperations: Total number of index operations that can execute simultaneously on one data node. Deprecated as of NDB 8.0.19.

  • MaxNoOfConcurrentTransactions: Maximum number of transactions executing concurrently on this data node, total number of transactions that can be executed concurrently is this value times number of data nodes in cluster. Deprecated as of NDB 8.0.19.

  • MaxNoOfFiredTriggers: Total number of triggers that can fire simultaneously on one data node. Deprecated as of NDB 8.0.19.

  • MaxNoOfLocalOperations: Maximum number of operation records defined on this data node. Deprecated as of NDB 8.0.19.

  • MaxNoOfLocalScans: Maximum number of fragment scans in parallel on this data node. Deprecated as of NDB 8.0.19.

  • ReservedTransactionBufferMemory: Dynamic buffer space (in bytes) for key and attribute data allocated to each data node. Deprecated as of NDB 8.0.19.

Node Configuration Parameters Removed in NDB 8.0

No node configuration parameters have been removed from NDB 8.0.

MySQL Server Options and Variables Introduced in NDB 8.0

The following mysqld system variables, status variables, and options have been added in NDB 8.0.

MySQL Server Options and Variables Deprecated in NDB 8.0

The following mysqld system variables, status variables, and options have been deprecated in NDB 8.0.

MySQL Server Options and Variables Removed in NDB 8.0

The following mysqld system variables, status variables, and options have been removed in NDB 8.0.

  • Ndb_metadata_blacklist_size: Number of NDB metadata objects that NDB binlog thread has failed to synchronize; renamed in NDB 8.0.22 as Ndb_metadata_excluded_count. Removed in NDB 8.0.22.

23.1.6 MySQL Server Using InnoDB Compared with NDB Cluster

MySQL Server offers a number of choices in storage engines. Since both NDB and InnoDB can serve as transactional MySQL storage engines, users of MySQL Server sometimes become interested in NDB Cluster. They see NDB as a possible alternative or upgrade to the default InnoDB storage engine in MySQL 8.0. While NDB and InnoDB share common characteristics, there are differences in architecture and implementation, so that some existing MySQL Server applications and usage scenarios can be a good fit for NDB Cluster, but not all of them.

In this section, we discuss and compare some characteristics of the NDB storage engine used by NDB 8.0 with InnoDB used in MySQL 8.0. The next few sections provide a technical comparison. In many instances, decisions about when and where to use NDB Cluster must be made on a case-by-case basis, taking all factors into consideration. While it is beyond the scope of this documentation to provide specifics for every conceivable usage scenario, we also attempt to offer some very general guidance on the relative suitability of some common types of applications for NDB as opposed to InnoDB back ends.

NDB Cluster 8.0 uses a mysqld based on MySQL 8.0, including support for InnoDB 1.1. While it is possible to use InnoDB tables with NDB Cluster, such tables are not clustered. It is also not possible to use programs or libraries from an NDB Cluster 8.0 distribution with MySQL Server 8.0, or the reverse.

While it is also true that some types of common business applications can be run either on NDB Cluster or on MySQL Server (most likely using the InnoDB storage engine), there are some important architectural and implementation differences. Section 23.1.6.1, “Differences Between the NDB and InnoDB Storage Engines”, provides a summary of the these differences. Due to the differences, some usage scenarios are clearly more suitable for one engine or the other; see Section 23.1.6.2, “NDB and InnoDB Workloads”. This in turn has an impact on the types of applications that better suited for use with NDB or InnoDB. See Section 23.1.6.3, “NDB and InnoDB Feature Usage Summary”, for a comparison of the relative suitability of each for use in common types of database applications.

For information about the relative characteristics of the NDB and MEMORY storage engines, see When to Use MEMORY or NDB Cluster.

See Chapter 16, Alternative Storage Engines, for additional information about MySQL storage engines.

23.1.6.1 Differences Between the NDB and InnoDB Storage Engines

The NDB storage engine is implemented using a distributed, shared-nothing architecture, which causes it to behave differently from InnoDB in a number of ways. For those unaccustomed to working with NDB, unexpected behaviors can arise due to its distributed nature with regard to transactions, foreign keys, table limits, and other characteristics. These are shown in the following table:

Table 23.2 Differences between InnoDB and NDB storage engines

Feature InnoDB (MySQL 8.0) NDB 8.0
MySQL Server Version 8.0 8.0
InnoDB Version InnoDB 8.0.24 InnoDB 8.0.24
NDB Cluster Version N/A NDB 8.0.23/8.0.23
Storage Limits 64TB 128TB
Foreign Keys Yes Yes
Transactions All standard types READ COMMITTED
MVCC Yes No
Data Compression Yes No (NDB checkpoint and backup files can be compressed)
Large Row Support (> 14K) Supported for VARBINARY, VARCHAR, BLOB, and TEXT columns Supported for BLOB and TEXT columns only (Using these types to store very large amounts of data can lower NDB performance)
Replication Support Asynchronous and semisynchronous replication using MySQL Replication; MySQL Group Replication Automatic synchronous replication within an NDB Cluster; asynchronous replication between NDB Clusters, using MySQL Replication (Semisynchronous replication is not supported)
Scaleout for Read Operations Yes (MySQL Replication) Yes (Automatic partitioning in NDB Cluster; NDB Cluster Replication)
Scaleout for Write Operations Requires application-level partitioning (sharding) Yes (Automatic partitioning in NDB Cluster is transparent to applications)
High Availability (HA) Built-in, from InnoDB cluster Yes (Designed for 99.999% uptime)
Node Failure Recovery and Failover From MySQL Group Replication Automatic (Key element in NDB architecture)
Time for Node Failure Recovery 30 seconds or longer Typically < 1 second
Real-Time Performance No Yes
In-Memory Tables No Yes (Some data can optionally be stored on disk; both in-memory and disk data storage are durable)
NoSQL Access to Storage Engine Yes Yes (Multiple APIs, including Memcached, Node.js/JavaScript, Java, JPA, C++, and HTTP/REST)
Concurrent and Parallel Writes Yes Up to 48 writers, optimized for concurrent writes
Conflict Detection and Resolution (Multiple Sources) Yes (MySQL Group Replication) Yes
Hash Indexes No Yes
Online Addition of Nodes Read/write replicas using MySQL Group Replication Yes (all node types)
Online Upgrades Yes (using replication) Yes
Online Schema Modifications Yes, as part of MySQL 8.0 Yes

23.1.6.2 NDB and InnoDB Workloads

NDB Cluster has a range of unique attributes that make it ideal to serve applications requiring high availability, fast failover, high throughput, and low latency. Due to its distributed architecture and multi-node implementation, NDB Cluster also has specific constraints that may keep some workloads from performing well. A number of major differences in behavior between the NDB and InnoDB storage engines with regard to some common types of database-driven application workloads are shown in the following table::

Table 23.3 Differences between InnoDB and NDB storage engines, common types of data-driven application workloads.

Workload InnoDB NDB Cluster (NDB)
High-Volume OLTP Applications Yes Yes
DSS Applications (data marts, analytics) Yes Limited (Join operations across OLTP datasets not exceeding 3TB in size)
Custom Applications Yes Yes
Packaged Applications Yes Limited (should be mostly primary key access); NDB Cluster 8.0 supports foreign keys
In-Network Telecoms Applications (HLR, HSS, SDP) No Yes
Session Management and Caching Yes Yes
E-Commerce Applications Yes Yes
User Profile Management, AAA Protocol Yes Yes

23.1.6.3 NDB and InnoDB Feature Usage Summary

When comparing application feature requirements to the capabilities of InnoDB with NDB, some are clearly more compatible with one storage engine than the other.

The following table lists supported application features according to the storage engine to which each feature is typically better suited.

Table 23.4 Supported application features according to the storage engine to which each feature is typically better suited

Preferred application requirements for InnoDB Preferred application requirements for NDB
  • Foreign keys

    Note

    NDB Cluster 8.0 supports foreign keys

  • Full table scans

  • Very large databases, rows, or transactions

  • Transactions other than READ COMMITTED

  • Write scaling

  • 99.999% uptime

  • Online addition of nodes and online schema operations

  • Multiple SQL and NoSQL APIs (see NDB Cluster APIs: Overview and Concepts)

  • Real-time performance

  • Limited use of BLOB columns

  • Foreign keys are supported, although their use may have an impact on performance at high throughput


23.1.7 Known Limitations of NDB Cluster

In the sections that follow, we discuss known limitations in current releases of NDB Cluster as compared with the features available when using the MyISAM and InnoDB storage engines. If you check the Cluster category in the MySQL bugs database at http://bugs.mysql.com, you can find known bugs in the following categories under MySQL Server: in the MySQL bugs database at http://bugs.mysql.com, which we intend to correct in upcoming releases of NDB Cluster:

  • NDB Cluster

  • Cluster Direct API (NDBAPI)

  • Cluster Disk Data

  • Cluster Replication

  • ClusterJ

This information is intended to be complete with respect to the conditions just set forth. You can report any discrepancies that you encounter to the MySQL bugs database using the instructions given in Section 1.6, “How to Report Bugs or Problems”. Any problem which we do not plan to fix in NDB Cluster 8.0, is added to the list.

See Section 23.1.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.0” for a list of issues in earlier releases that have been resolved in NDB Cluster 8.0.

Note

Limitations and other issues specific to NDB Cluster Replication are described in Section 23.6.3, “Known Issues in NDB Cluster Replication”.

23.1.7.1 Noncompliance with SQL Syntax in NDB Cluster

Some SQL statements relating to certain MySQL features produce errors when used with NDB tables, as described in the following list:

  • Temporary tables.  Temporary tables are not supported. Trying either to create a temporary table that uses the NDB storage engine or to alter an existing temporary table to use NDB fails with the error Table storage engine 'ndbcluster' does not support the create option 'TEMPORARY'.

  • Indexes and keys in NDB tables.  Keys and indexes on NDB Cluster tables are subject to the following limitations:

    • Column width.  Attempting to create an index on an NDB table column whose width is greater than 3072 bytes succeeds, but only the first 3072 bytes are actually used for the index. In such cases, a warning Specified key was too long; max key length is 3072 bytes is issued, and a SHOW CREATE TABLE statement shows the length of the index as 3072.

    • TEXT and BLOB columns.  You cannot create indexes on NDB table columns that use any of the TEXT or BLOB data types.

    • FULLTEXT indexes.  The NDB storage engine does not support FULLTEXT indexes, which are possible for MyISAM and InnoDB tables only.

      However, you can create indexes on VARCHAR columns of NDB tables.

    • USING HASH keys and NULL.  Using nullable columns in unique keys and primary keys means that queries using these columns are handled as full table scans. To work around this issue, make the column NOT NULL, or re-create the index without the USING HASH option.

    • Prefixes.  There are no prefix indexes; only entire columns can be indexed. (The size of an NDB column index is always the same as the width of the column in bytes, up to and including 3072 bytes, as described earlier in this section. Also see Section 23.1.7.6, “Unsupported or Missing Features in NDB Cluster”, for additional information.)

    • BIT columns.  A BIT column cannot be a primary key, unique key, or index, nor can it be part of a composite primary key, unique key, or index.

    • AUTO_INCREMENT columns.  Like other MySQL storage engines, the NDB storage engine can handle a maximum of one AUTO_INCREMENT column per table. However, in the case of an NDB table with no explicit primary key, an AUTO_INCREMENT column is automatically defined and used as a hidden primary key. For this reason, you cannot define a table that has an explicit AUTO_INCREMENT column unless that column is also declared using the PRIMARY KEY option. Attempting to create a table with an AUTO_INCREMENT column that is not the table's primary key, and using the NDB storage engine, fails with an error.

  • Restrictions on foreign keys.  Support for foreign key constraints in NDB 8.0 is comparable to that provided by InnoDB, subject to the following restrictions:

    • Every column referenced as a foreign key requires an explicit unique key, if it is not the table's primary key.

    • ON UPDATE CASCADE is not supported when the reference is to the parent table's primary key.

      This is because an update of a primary key is implemented as a delete of the old row (containing the old primary key) plus an insert of the new row (with a new primary key). This is not visible to the NDB kernel, which views these two rows as being the same, and thus has no way of knowing that this update should be cascaded.

    • As of NDB 8.0.16: ON DELETE CASCADE is not supported where the child table contains one or more columns of any of the TEXT or BLOB types. (Bug #89511, Bug #27484882)

    • SET DEFAULT is not supported. (Also not supported by InnoDB.)

    • The NO ACTION keyword is accepted but treated as RESTRICT. NO ACTION, which is a standard SQL keyword, is the default in MySQL 8.0. (Also the same as with InnoDB.)

    • In earlier versions of NDB Cluster, when creating a table with foreign key referencing an index in another table, it sometimes appeared possible to create the foreign key even if the order of the columns in the indexes did not match, due to the fact that an appropriate error was not always returned internally. A partial fix for this issue improved the error used internally to work in most cases; however, it remains possible for this situation to occur in the event that the parent index is a unique index. (Bug #18094360)

    For more information, see Section 13.1.20.5, “FOREIGN KEY Constraints”, and Section 1.7.3.2, “FOREIGN KEY Constraints”.

  • NDB Cluster and geometry data types.  Geometry data types (WKT and WKB) are supported for NDB tables. However, spatial indexes are not supported.

  • Character sets and binary log files.  Currently, the ndb_apply_status and ndb_binlog_index tables are created using the latin1 (ASCII) character set. Because names of binary logs are recorded in this table, binary log files named using non-Latin characters are not referenced correctly in these tables. This is a known issue, which we are working to fix. (Bug #50226)

    To work around this problem, use only Latin-1 characters when naming binary log files or setting any the --basedir, --log-bin, or --log-bin-index options.

  • Creating NDB tables with user-defined partitioning.  Support for user-defined partitioning in NDB Cluster is restricted to [LINEAR] KEY partitioning. Using any other partitioning type with ENGINE=NDB or ENGINE=NDBCLUSTER in a CREATE TABLE statement results in an error.

    It is possible to override this restriction, but doing so is not supported for use in production settings. For details, see User-defined partitioning and the NDB storage engine (NDB Cluster).

    Default partitioning scheme.  All NDB Cluster tables are by default partitioned by KEY using the table's primary key as the partitioning key. If no primary key is explicitly set for the table, the hidden primary key automatically created by the NDB storage engine is used instead. For additional discussion of these and related issues, see Section 24.2.5, “KEY Partitioning”.

    CREATE TABLE and ALTER TABLE statements that would cause a user-partitioned NDBCLUSTER table not to meet either or both of the following two requirements are not permitted, and fail with an error:

    1. The table must have an explicit primary key.

    2. All columns listed in the table's partitioning expression must be part of the primary key.

    Exception.  If a user-partitioned NDBCLUSTER table is created using an empty column-list (that is, using PARTITION BY [LINEAR] KEY()), then no explicit primary key is required.

    Maximum number of partitions for NDBCLUSTER tables.  The maximum number of partitions that can defined for a NDBCLUSTER table when employing user-defined partitioning is 8 per node group. (See Section 23.1.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”, for more information about NDB Cluster node groups.

    DROP PARTITION not supported.  It is not possible to drop partitions from NDB tables using ALTER TABLE ... DROP PARTITION. The other partitioning extensions to ALTER TABLEADD PARTITION, REORGANIZE PARTITION, and COALESCE PARTITION—are supported for NDB tables, but use copying and so are not optimized. See Section 24.3.1, “Management of RANGE and LIST Partitions” and Section 13.1.9, “ALTER TABLE Statement”.

  • Row-based replication.  When using row-based replication with NDB Cluster, binary logging cannot be disabled. That is, the NDB storage engine ignores the value of sql_log_bin.

  • JSON data type.  The MySQL JSON data type is supported for NDB tables in the mysqld supplied with NDB 8.0.

    An NDB table can have a maximum of 3 JSON columns.

    The NDB API has no special provision for working with JSON data, which it views simply as BLOB data. Handling data as JSON must be performed by the application.

23.1.7.2 Limits and Differences of NDB Cluster from Standard MySQL Limits

In this section, we list limits found in NDB Cluster that either differ from limits found in, or that are not found in, standard MySQL.

Memory usage and recovery.  Memory consumed when data is inserted into an NDB table is not automatically recovered when deleted, as it is with other storage engines. Instead, the following rules hold true:

  • A DELETE statement on an NDB table makes the memory formerly used by the deleted rows available for re-use by inserts on the same table only. However, this memory can be made available for general re-use by performing OPTIMIZE TABLE.

    A rolling restart of the cluster also frees any memory used by deleted rows. See Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”.

  • A DROP TABLE or TRUNCATE TABLE operation on an NDB table frees the memory that was used by this table for re-use by any NDB table, either by the same table or by another NDB table.

    Note

    Recall that TRUNCATE TABLE drops and re-creates the table. See Section 13.1.37, “TRUNCATE TABLE Statement”.

  • Limits imposed by the cluster's configuration.  A number of hard limits exist which are configurable, but available main memory in the cluster sets limits. See the complete list of configuration parameters in Section 23.3.3, “NDB Cluster Configuration Files”. Most configuration parameters can be upgraded online. These hard limits include:

  • Node and data object maximums.  The following limits apply to numbers of cluster nodes and metadata objects:

    • As of NDB 8.0.18, the maximum number of data nodes is 145. (Previously, this was 48.)

      A data node must have a node ID in the range of 1 to 144, inclusive. (In NDB 8.0.17 and earlier releases, this was 1 to 48, inclusive.)

      Management and API nodes may use node IDs in the range 1 to 255, inclusive.

    • The total maximum number of nodes in an NDB Cluster is 255. This number includes all SQL nodes (MySQL Servers), API nodes (applications accessing the cluster other than MySQL servers), data nodes, and management servers.

    • The maximum number of metadata objects in current versions of NDB Cluster is 20320. This limit is hard-coded.

    See Section 23.1.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.0”, for more information.

23.1.7.3 Limits Relating to Transaction Handling in NDB Cluster

A number of limitations exist in NDB Cluster with regard to the handling of transactions. These include the following:

  • Transaction isolation level.  The NDBCLUSTER storage engine supports only the READ COMMITTED transaction isolation level. (InnoDB, for example, supports READ COMMITTED, READ UNCOMMITTED, REPEATABLE READ, and SERIALIZABLE.) You should keep in mind that NDB implements READ COMMITTED on a per-row basis; when a read request arrives at the data node storing the row, what is returned is the last committed version of the row at that time.

    Uncommitted data is never returned, but when a transaction modifying a number of rows commits concurrently with a transaction reading the same rows, the transaction performing the read can observe before values, after values, or both, for different rows among these, due to the fact that a given row read request can be processed either before or after the commit of the other transaction.

    To ensure that a given transaction reads only before or after values, you can impose row locks using SELECT ... LOCK IN SHARE MODE. In such cases, the lock is held until the owning transaction is committed. Using row locks can also cause the following issues:

    • Increased frequency of lock wait timeout errors, and reduced concurrency

    • Increased transaction processing overhead due to reads requiring a commit phase

    • Possibility of exhausting the available number of concurrent locks, which is limited by MaxNoOfConcurrentOperations

    NDB uses READ COMMITTED for all reads unless a modifier such as LOCK IN SHARE MODE or FOR UPDATE is used. LOCK IN SHARE MODE causes shared row locks to be used; FOR UPDATE causes exclusive row locks to be used. Unique key reads have their locks upgraded automatically by NDB to ensure a self-consistent read; BLOB reads also employ extra locking for consistency.

    See Section 23.5.8.4, “NDB Cluster Backup Troubleshooting”, for information on how NDB Cluster's implementation of transaction isolation level can affect backup and restoration of NDB databases.

  • Transactions and BLOB or TEXT columns.  NDBCLUSTER stores only part of a column value that uses any of MySQL's BLOB or TEXT data types in the table visible to MySQL; the remainder of the BLOB or TEXT is stored in a separate internal table that is not accessible to MySQL. This gives rise to two related issues of which you should be aware whenever executing SELECT statements on tables that contain columns of these types:

    1. For any SELECT from an NDB Cluster table: If the SELECT includes a BLOB or TEXT column, the READ COMMITTED transaction isolation level is converted to a read with read lock. This is done to guarantee consistency.

    2. For any SELECT which uses a unique key lookup to retrieve any columns that use any of the BLOB or TEXT data types and that is executed within a transaction, a shared read lock is held on the table for the duration of the transaction—that is, until the transaction is either committed or aborted.

      This issue does not occur for queries that use index or table scans, even against NDB tables having BLOB or TEXT columns.

      For example, consider the table t defined by the following CREATE TABLE statement:

      CREATE TABLE t (
          a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
          b INT NOT NULL,
          c INT NOT NULL,
          d TEXT,
          INDEX i(b),
          UNIQUE KEY u(c)
      ) ENGINE = NDB,
      

      The following query on t causes a shared read lock, because it uses a unique key lookup:

      SELECT * FROM t WHERE c = 1;
      

      However, none of the four queries shown here causes a shared read lock:

      SELECT * FROM t WHERE b = 1;
      
      SELECT * FROM t WHERE d = '1';
      
      SELECT * FROM t;
      
      SELECT b,c WHERE a = 1;
      

      This is because, of these four queries, the first uses an index scan, the second and third use table scans, and the fourth, while using a primary key lookup, does not retrieve the value of any BLOB or TEXT columns.

      You can help minimize issues with shared read locks by avoiding queries that use unique key lookups that retrieve BLOB or TEXT columns, or, in cases where such queries are not avoidable, by committing transactions as soon as possible afterward.

  • Unique key lookups and transaction isolation.  Unique indexes are implemented in NDB using a hidden index table which is maintained internally. When a user-created NDB table is accessed using a unique index, the hidden index table is first read to find the primary key that is then used to read the user-created table. To avoid modification of the index during this double-read operation, the row found in the hidden index table is locked. When a row referenced by a unique index in the user-created NDB table is updated, the hidden index table is subject to an exclusive lock by the transaction in which the update is performed. This means that any read operation on the same (user-created) NDB table must wait for the update to complete. This is true even when the transaction level of the read operation is READ COMMITTED.

    One workaround which can be used to bypass potentially blocking reads is to force the SQL node to ignore the unique index when performing the read. This can be done by using the IGNORE INDEX index hint as part of the SELECT statement reading the table (see Section 8.9.4, “Index Hints”). Because the MySQL server creates a shadowing ordered index for every unique index created in NDB, this lets the ordered index be read instead, and avoids unique index access locking. The resulting read is as consistent as a committed read by primary key, returning the last committed value at the time the row is read.

    Reading via an ordered index makes less efficient use of resources in the cluster, and may have higher latency.

    It is also possible to avoid using the unique index for access by querying for ranges rather than for unique values.

  • Rollbacks.  There are no partial transactions, and no partial rollbacks of transactions. A duplicate key or similar error causes the entire transaction to be rolled back.

    This behavior differs from that of other transactional storage engines such as InnoDB that may roll back individual statements.

  • Transactions and memory usage.  As noted elsewhere in this chapter, NDB Cluster does not handle large transactions well; it is better to perform a number of small transactions with a few operations each than to attempt a single large transaction containing a great many operations. Among other considerations, large transactions require very large amounts of memory. Because of this, the transactional behavior of a number of MySQL statements is affected as described in the following list:

    • TRUNCATE TABLE is not transactional when used on NDB tables. If a TRUNCATE TABLE fails to empty the table, then it must be re-run until it is successful.

    • DELETE FROM (even with no WHERE clause) is transactional. For tables containing a great many rows, you may find that performance is improved by using several DELETE FROM ... LIMIT ... statements to chunk the delete operation. If your objective is to empty the table, then you may wish to use TRUNCATE TABLE instead.

    • LOAD DATA statements.  LOAD DATA is not transactional when used on NDB tables.

      Important

      When executing a LOAD DATA statement, the NDB engine performs commits at irregular intervals that enable better utilization of the communication network. It is not possible to know ahead of time when such commits take place.

    • ALTER TABLE and transactions.  When copying an NDB table as part of an ALTER TABLE, the creation of the copy is nontransactional. (In any case, this operation is rolled back when the copy is deleted.)

  • Transactions and the COUNT() function.  When using NDB Cluster Replication, it is not possible to guarantee the transactional consistency of the COUNT() function on the replica. In other words, when performing on the source a series of statements (INSERT, DELETE, or both) that changes the number of rows in a table within a single transaction, executing SELECT COUNT(*) FROM table queries on the replica may yield intermediate results. This is due to the fact that SELECT COUNT(...) may perform dirty reads, and is not a bug in the NDB storage engine. (See Bug #31321 for more information.)

23.1.7.4 NDB Cluster Error Handling

Starting, stopping, or restarting a node may give rise to temporary errors causing some transactions to fail. These include the following cases:

  • Temporary errors.  When first starting a node, it is possible that you may see Error 1204 Temporary failure, distribution changed and similar temporary errors.

  • Errors due to node failure.  The stopping or failure of any data node can result in a number of different node failure errors. (However, there should be no aborted transactions when performing a planned shutdown of the cluster.)

In either of these cases, any errors that are generated must be handled within the application. This should be done by retrying the transaction.

See also Section 23.1.7.2, “Limits and Differences of NDB Cluster from Standard MySQL Limits”.

23.1.7.5 Limits Associated with Database Objects in NDB Cluster

Some database objects such as tables and indexes have different limitations when using the NDBCLUSTER storage engine:

  • Number of database objects.  The maximum number of all NDB database objects in a single NDB Cluster—including databases, tables, and indexes—is limited to 20320.

  • Attributes per table.  The maximum number of attributes (that is, columns and indexes) that can belong to a given table is 512.

  • Attributes per key.  The maximum number of attributes per key is 32.

  • Row size.  Beginning with NDB 8.0.18, the maximum permitted size of any one row is 30000 bytes, in NDB 8.0.17 and earlier releases, this limit is 14000 bytes.

    Each BLOB or TEXT column contributes 256 + 8 = 264 bytes to this total; this includes JSON columns. See String Type Storage Requirements, as well as JSON Storage Requirements, for more information relating to these types.

    In addition, the maximum offset for a fixed-width column of an NDB table is 8188 bytes; attempting to create a table that violates this limitation fails with NDB error 851 Maximum offset for fixed-size columns exceeded. For memory-based columns, you can work around this limitation by using a variable-width column type such as VARCHAR or defining the column as COLUMN_FORMAT=DYNAMIC; this does not work with columns stored on disk. For disk-based columns, you may be able to do so by reordering one or more of the table's disk-based columns such that the combined width of all but the disk-based column defined last in the CREATE TABLE statement used to create the table does not exceed 8188 bytes, less any possible rounding performed for some data types such as CHAR or VARCHAR; otherwise it is necessary to use memory-based storage for one or more of the offending column or columns instead.

  • BIT column storage per table.  The maximum combined width for all BIT columns used in a given NDB table is 4096.

  • FIXED column storage.  NDB Cluster 8.0 supports a maximum of 128 TB per fragment of data in FIXED columns.

23.1.7.6 Unsupported or Missing Features in NDB Cluster

A number of features supported by other storage engines are not supported for NDB tables. Trying to use any of these features in NDB Cluster does not cause errors in or of itself; however, errors may occur in applications that expects the features to be supported or enforced. Statements referencing such features, even if effectively ignored by NDB, must be syntactically and otherwise valid.

  • Index prefixes.  Prefixes on indexes are not supported for NDB tables. If a prefix is used as part of an index specification in a statement such as CREATE TABLE, ALTER TABLE, or CREATE INDEX, the prefix is not created by NDB.

    A statement containing an index prefix, and creating or modifying an NDB table, must still be syntactically valid. For example, the following statement always fails with Error 1089 Incorrect prefix key; the used key part isn't a string, the used length is longer than the key part, or the storage engine doesn't support unique prefix keys, regardless of storage engine:

    CREATE TABLE t1 (
        c1 INT NOT NULL,
        c2 VARCHAR(100),
        INDEX i1 (c2(500))
    );

    This happens on account of the SQL syntax rule that no index may have a prefix larger than itself.

  • Savepoints and rollbacks.  Savepoints and rollbacks to savepoints are ignored as in MyISAM.

  • Durability of commits.  There are no durable commits on disk. Commits are replicated, but there is no guarantee that logs are flushed to disk on commit.

  • Replication.  Statement-based replication is not supported. Use --binlog-format=ROW (or --binlog-format=MIXED) when setting up cluster replication. See Section 23.6, “NDB Cluster Replication”, for more information.

    Replication using global transaction identifiers (GTIDs) is not compatible with NDB Cluster, and is not supported in NDB Cluster 8.0. Do not enable GTIDs when using the NDB storage engine, as this is very likely to cause problems up to and including failure of NDB Cluster Replication.

    Semisynchronous replication is not supported in NDB Cluster.

  • Generated columns.  The NDB storage engine does not support indexes on virtual generated columns.

    As with other storage engines, you can create an index on a stored generated column, but you should bear in mind that NDB uses DataMemory for storage of the generated column as well as IndexMemory for the index. See JSON columns and indirect indexing in NDB Cluster, for an example.

    NDB Cluster writes changes in stored generated columns to the binary log, but does log not those made to virtual columns. This should not effect NDB Cluster Replication or replication between NDB and other MySQL storage engines.

Note

See Section 23.1.7.3, “Limits Relating to Transaction Handling in NDB Cluster”, for more information relating to limitations on transaction handling in NDB.

23.1.7.7 Limitations Relating to Performance in NDB Cluster

The following performance issues are specific to or especially pronounced in NDB Cluster:

  • Range scans.  There are query performance issues due to sequential access to the NDB storage engine; it is also relatively more expensive to do many range scans than it is with either MyISAM or InnoDB.

  • Reliability of Records in range.  The Records in range statistic is available but is not completely tested or officially supported. This may result in nonoptimal query plans in some cases. If necessary, you can employ USE INDEX or FORCE INDEX to alter the execution plan. See Section 8.9.4, “Index Hints”, for more information on how to do this.

  • Unique hash indexes.  Unique hash indexes created with USING HASH cannot be used for accessing a table if NULL is given as part of the key.

23.1.7.8 Issues Exclusive to NDB Cluster

The following are limitations specific to the NDB storage engine:

  • Machine architecture.  All machines used in the cluster must have the same architecture. That is, all machines hosting nodes must be either big-endian or little-endian, and you cannot use a mixture of both. For example, you cannot have a management node running on a PowerPC which directs a data node that is running on an x86 machine. This restriction does not apply to machines simply running mysql or other clients that may be accessing the cluster's SQL nodes.

  • Binary logging.  NDB Cluster has the following limitations or restrictions with regard to binary logging:

  • Schema operations.  Schema operations (DDL statements) are rejected while any data node restarts. Schema operations are also not supported while performing an online upgrade or downgrade.

  • Number of fragment replicas.  The number of fragment replicas, as determined by the NoOfReplicas data node configuration parameter, is the number of copies of all data stored by NDB Cluster. Setting this parameter to 1 means there is only a single copy; in this case, no redundancy is provided, and the loss of a data node entails loss of data. To guarantee redundancy, and thus preservation of data even if a data node fails, set this parameter to 2, which is the default and recommended value in production.

    Setting NoOfReplicas to a value greater than 2 is supported (to a maximum of 4) but unnecessary to guard against loss of data.

See also Section 23.1.7.10, “Limitations Relating to Multiple NDB Cluster Nodes”.

23.1.7.9 Limitations Relating to NDB Cluster Disk Data Storage

Disk Data object maximums and minimums.  Disk data objects are subject to the following maximums and minimums:

  • Maximum number of tablespaces: 232 (4294967296)

  • Maximum number of data files per tablespace: 216 (65536)

  • The minimum and maximum possible sizes of extents for tablespace data files are 32K and 2G, respectively. See Section 13.1.21, “CREATE TABLESPACE Statement”, for more information.

In addition, when working with NDB Disk Data tables, you should be aware of the following issues regarding data files and extents:

  • Data files use DataMemory. Usage is the same as for in-memory data.

  • Data files use file descriptors. It is important to keep in mind that data files are always open, which means the file descriptors are always in use and cannot be re-used for other system tasks.

  • Extents require sufficient DiskPageBufferMemory; you must reserve enough for this parameter to account for all memory used by all extents (number of extents times size of extents).

Disk Data tables and diskless mode.  Use of Disk Data tables is not supported when running the cluster in diskless mode.

23.1.7.10 Limitations Relating to Multiple NDB Cluster Nodes

Multiple SQL nodes.  The following are issues relating to the use of multiple MySQL servers as NDB Cluster SQL nodes, and are specific to the NDBCLUSTER storage engine:

  • Stored programs not distributed.  Stored procedures, stored functions, triggers, and scheduled events are all supported by tables using the NDB storage engine, but these do not propagate automatically between MySQL Servers acting as Cluster SQL nodes, and must be re-created separately on each SQL node. See Stored routines and triggers in NDB Cluster.

  • No distributed table locks.  A LOCK TABLES works only for the SQL node on which the lock is issued; no other SQL node in the cluster sees this lock. This is also true for a lock issued by any statement that locks tables as part of its operations. (See next item for an example.)

  • ALTER TABLE operations.  ALTER TABLE is not fully locking when running multiple MySQL servers (SQL nodes). (As discussed in the previous item, NDB Cluster does not support distributed table locks.)

Multiple management nodes.  When using multiple management servers:

  • If any of the management servers are running on the same host, you must give nodes explicit IDs in connection strings because automatic allocation of node IDs does not work across multiple management servers on the same host. This is not required if every management server resides on a different host.

  • When a management server starts, it first checks for any other management server in the same NDB Cluster, and upon successful connection to the other management server uses its configuration data. This means that the management server --reload and --initial startup options are ignored unless the management server is the only one running. It also means that, when performing a rolling restart of an NDB Cluster with multiple management nodes, the management server reads its own configuration file if (and only if) it is the only management server running in this NDB Cluster. See Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”, for more information.

Multiple network addresses.  Multiple network addresses per data node are not supported. Use of these is liable to cause problems: In the event of a data node failure, an SQL node waits for confirmation that the data node went down but never receives it because another route to that data node remains open. This can effectively make the cluster inoperable.

Note

It is possible to use multiple network hardware interfaces (such as Ethernet cards) for a single data node, but these must be bound to the same address. This also means that it not possible to use more than one [tcp] section per connection in the config.ini file. See Section 23.3.3.10, “NDB Cluster TCP/IP Connections”, for more information.

23.1.7.11 Previous NDB Cluster Issues Resolved in NDB Cluster 8.0

A number of limitations and related issues that existed in earlier versions of NDB Cluster have been resolved in NDB 8.0. These are described briefly in the following list:

  • Database and table names.  Prior to NDB 8.0.18, when using the NDB storage engine, the maximum allowed length both for database names and for table names is 63 characters, and a statement using a database name or table name longer than this limit failed with an appropriate error. As of NDB 8.0.18, this restriction is lifted and identifiers for NDB databases and tables may now use up to 64 bytes, as with other MySQL database and table names.

  • IPv6 support.  Prior to NDB 8.0.22, it was necessary for all network addresses used for connections between nodes within an NDB Cluster to use or to be resolvable to IPv4 addresses. Beginning with NDB 8.0.22, NDB supports IPv6 addresses for all types of cluster nodes, as well as for applications that use the NDB API or MGM API.

23.2 NDB Cluster Installation

This section describes the basics for planning, installing, configuring, and running an NDB Cluster. Whereas the examples in Section 23.3, “Configuration of NDB Cluster” provide more in-depth information on a variety of clustering options and configuration, the result of following the guidelines and procedures outlined here should be a usable NDB Cluster which meets the minimum requirements for availability and safeguarding of data.

For information about upgrading or downgrading an NDB Cluster between release versions, see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”.

This section covers hardware and software requirements; networking issues; installation of NDB Cluster; basic configuration issues; starting, stopping, and restarting the cluster; loading of a sample database; and performing queries.

NDB Cluster also provides the NDB Cluster Auto-Installer (now deprecated), a web-based graphical installer, as part of the NDB Cluster distribution. The Auto-Installer can be used to perform basic installation and setup of an NDB Cluster on one (for testing) or more host computers. See Section 23.2.8, “The NDB Cluster Auto-Installer (No longer supported)”, for more information.

Assumptions.  The following sections make a number of assumptions regarding the cluster's physical and network configuration. These assumptions are discussed in the next few paragraphs.

Cluster nodes and host computers.  The cluster consists of four nodes, each on a separate host computer, and each with a fixed network address on a typical Ethernet network as shown here:

Table 23.5 Network addresses of nodes in example cluster

Node IP Address
Management node (mgmd) 198.51.100.10
SQL node (mysqld) 198.51.100.20
Data node "A" (ndbd) 198.51.100.30
Data node "B" (ndbd) 198.51.100.40

This setup is also shown in the following diagram:

Figure 23.4 NDB Cluster Multi-Computer Setup

Most content is described in the surrounding text. The four nodes each connect to a central switch that connects to a network.

Network addressing.  In the interest of simplicity (and reliability), this How-To uses only numeric IP addresses. However, if DNS resolution is available on your network, it is possible to use host names in lieu of IP addresses in configuring Cluster. Alternatively, you can use the hosts file (typically /etc/hosts for Linux and other Unix-like operating systems, C:\WINDOWS\system32\drivers\etc\hosts on Windows, or your operating system's equivalent) for providing a means to do host lookup if such is available.

Prior to NDB 8.0.22, all network addresses used for connections to or from data and management nodes must use or be resolvable using IPv4. This includes addresses used by SQL nodes to contact the other nodes. Beginning with NDB 8.0.22, NDB Cluster supports IPv6 for connections between any and all cluster nodes.

Potential hosts file issues.  A common problem when trying to use host names for Cluster nodes arises because of the way in which some operating systems (including some Linux distributions) set up the system's own host name in the /etc/hosts during installation. Consider two machines with the host names ndb1 and ndb2, both in the cluster network domain. Red Hat Linux (including some derivatives such as CentOS and Fedora) places the following entries in these machines' /etc/hosts files:

#  ndb1 /etc/hosts:
127.0.0.1   ndb1.cluster ndb1 localhost.localdomain localhost
#  ndb2 /etc/hosts:
127.0.0.1   ndb2.cluster ndb2 localhost.localdomain localhost

SUSE Linux (including OpenSUSE) places these entries in the machines' /etc/hosts files:

#  ndb1 /etc/hosts:
127.0.0.1       localhost
127.0.0.2       ndb1.cluster ndb1
#  ndb2 /etc/hosts:
127.0.0.1       localhost
127.0.0.2       ndb2.cluster ndb2

In both instances, ndb1 routes ndb1.cluster to a loopback IP address, but gets a public IP address from DNS for ndb2.cluster, while ndb2 routes ndb2.cluster to a loopback address and obtains a public address for ndb1.cluster. The result is that each data node connects to the management server, but cannot tell when any other data nodes have connected, and so the data nodes appear to hang while starting.

Caution

You cannot mix localhost and other host names or IP addresses in config.ini. For these reasons, the solution in such cases (other than to use IP addresses for all config.ini HostName entries) is to remove the fully qualified host names from /etc/hosts and use these in config.ini for all cluster hosts.

Host computer type.  Each host computer in our installation scenario is an Intel-based desktop PC running a supported operating system installed to disk in a standard configuration, and running no unnecessary services. The core operating system with standard TCP/IP networking capabilities should be sufficient. Also for the sake of simplicity, we also assume that the file systems on all hosts are set up identically. In the event that they are not, you should adapt these instructions accordingly.

Network hardware.  Standard 100 Mbps or 1 gigabit Ethernet cards are installed on each machine, along with the proper drivers for the cards, and that all four hosts are connected through a standard-issue Ethernet networking appliance such as a switch. (All machines should use network cards with the same throughput. That is, all four machines in the cluster should have 100 Mbps cards or all four machines should have 1 Gbps cards.) NDB Cluster works in a 100 Mbps network; however, gigabit Ethernet provides better performance.

Important

NDB Cluster is not intended for use in a network for which throughput is less than 100 Mbps or which experiences a high degree of latency. For this reason (among others), attempting to run an NDB Cluster over a wide area network such as the Internet is not likely to be successful, and is not supported in production.

Sample data.  We use the world database which is available for download from the MySQL website (see https://dev.mysql.com/doc/index-other.html). We assume that each machine has sufficient memory for running the operating system, required NDB Cluster processes, and (on the data nodes) storing the database.

For general information about installing MySQL, see Chapter 2, Installing and Upgrading MySQL. For information about installation of NDB Cluster on Linux and other Unix-like operating systems, see Section 23.2.1, “Installation of NDB Cluster on Linux”. For information about installation of NDB Cluster on Windows operating systems, see Section 23.2.2, “Installing NDB Cluster on Windows”.

For general information about NDB Cluster hardware, software, and networking requirements, see Section 23.1.3, “NDB Cluster Hardware, Software, and Networking Requirements”.

23.2.1 Installation of NDB Cluster on Linux

This section covers installation methods for NDB Cluster on Linux and other Unix-like operating systems. While the next few sections refer to a Linux operating system, the instructions and procedures given there should be easily adaptable to other supported Unix-like platforms. For manual installation and setup instructions specific to Windows systems, see Section 23.2.2, “Installing NDB Cluster on Windows”.

Each NDB Cluster host computer must have the correct executable programs installed. A host running an SQL node must have installed on it a MySQL Server binary (mysqld). Management nodes require the management server daemon (ndb_mgmd); data nodes require the data node daemon (ndbd or ndbmtd). It is not necessary to install the MySQL Server binary on management node hosts and data node hosts. It is recommended that you also install the management client (ndb_mgm) on the management server host.

Installation of NDB Cluster on Linux can be done using precompiled binaries from Oracle (downloaded as a .tar.gz archive), with RPM packages (also available from Oracle), or from source code. All three of these installation methods are described in the section that follow.

Regardless of the method used, it is still necessary following installation of the NDB Cluster binaries to create configuration files for all cluster nodes, before you can start the cluster. See Section 23.2.3, “Initial Configuration of NDB Cluster”.

23.2.1.1 Installing an NDB Cluster Binary Release on Linux

This section covers the steps necessary to install the correct executables for each type of Cluster node from precompiled binaries supplied by Oracle.

For setting up a cluster using precompiled binaries, the first step in the installation process for each cluster host is to download the binary archive from the NDB Cluster downloads page. (For the most recent 64-bit NDB 8.0 release, this is mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64.tar.gz.) We assume that you have placed this file in each machine's /var/tmp directory.

If you require a custom binary, see Section 2.9.5, “Installing MySQL Using a Development Source Tree”.

Note

After completing the installation, do not yet start any of the binaries. We show you how to do so following the configuration of the nodes (see Section 23.2.3, “Initial Configuration of NDB Cluster”).

SQL nodes.  On each of the machines designated to host SQL nodes, perform the following steps as the system root user:

  1. Check your /etc/passwd and /etc/group files (or use whatever tools are provided by your operating system for managing users and groups) to see whether there is already a mysql group and mysql user on the system. Some OS distributions create these as part of the operating system installation process. If they are not already present, create a new mysql user group, and then add a mysql user to this group:

    shell> groupadd mysql
    shell> useradd -g mysql -s /bin/false mysql
    

    The syntax for useradd and groupadd may differ slightly on different versions of Unix, or they may have different names such as adduser and addgroup.

  2. Change location to the directory containing the downloaded file, unpack the archive, and create a symbolic link named mysql to the mysql directory.

    Note

    The actual file and directory names vary according to the NDB Cluster version number.

    shell> cd /var/tmp
    shell> tar -C /usr/local -xzvf mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64.tar.gz
    shell> ln -s /usr/local/mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64 /usr/local/mysql
    
  3. Change location to the mysql directory and set up the system databases using mysqld --initialize as shown here:

    shell> cd mysql
    shell> mysqld --initialize
    

    This generates a random password for the MySQL root account. If you do not want the random password to be generated, you can substitute the --initialize-insecure option for --initialize. In either case, you should review Section 2.10.1, “Initializing the Data Directory”, for additional information before performing this step. See also Section 4.4.2, “mysql_secure_installation — Improve MySQL Installation Security”.

  4. Set the necessary permissions for the MySQL server and data directories:

    shell> chown -R root .
    shell> chown -R mysql data
    shell> chgrp -R mysql .
    
  5. Copy the MySQL startup script to the appropriate directory, make it executable, and set it to start when the operating system is booted up:

    shell> cp support-files/mysql.server /etc/rc.d/init.d/
    shell> chmod +x /etc/rc.d/init.d/mysql.server
    shell> chkconfig --add mysql.server
    

    (The startup scripts directory may vary depending on your operating system and version—for example, in some Linux distributions, it is /etc/init.d.)

    Here we use Red Hat's chkconfig for creating links to the startup scripts; use whatever means is appropriate for this purpose on your platform, such as update-rc.d on Debian.

Remember that the preceding steps must be repeated on each machine where an SQL node is to reside.

Data nodes.  Installation of the data nodes does not require the mysqld binary. Only the NDB Cluster data node executable ndbd (single-threaded) or ndbmtd (multithreaded) is required. These binaries can also be found in the .tar.gz archive. Again, we assume that you have placed this archive in /var/tmp.

As system root (that is, after using sudo, su root, or your system's equivalent for temporarily assuming the system administrator account's privileges), perform the following steps to install the data node binaries on the data node hosts:

  1. Change location to the /var/tmp directory, and extract the ndbd and ndbmtd binaries from the archive into a suitable directory such as /usr/local/bin:

    shell> cd /var/tmp
    shell> tar -zxvf mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64.tar.gz
    shell> cd mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64
    shell> cp bin/ndbd /usr/local/bin/ndbd
    shell> cp bin/ndbmtd /usr/local/bin/ndbmtd
    

    (You can safely delete the directory created by unpacking the downloaded archive, and the files it contains, from /var/tmp once ndb_mgm and ndb_mgmd have been copied to the executables directory.)

  2. Change location to the directory into which you copied the files, and then make both of them executable:

    shell> cd /usr/local/bin
    shell> chmod +x ndb*
    

The preceding steps should be repeated on each data node host.

Although only one of the data node executables is required to run an NDB Cluster data node, we have shown you how to install both ndbd and ndbmtd in the preceding instructions. We recommend that you do this when installing or upgrading NDB Cluster, even if you plan to use only one of them, since this saves time and trouble in the event that you later decide to change from one to the other.

Note

The data directory on each machine hosting a data node is /usr/local/mysql/data. This piece of information is essential when configuring the management node. (See Section 23.2.3, “Initial Configuration of NDB Cluster”.)

Management nodes.  Installation of the management node does not require the mysqld binary. Only the NDB Cluster management server (ndb_mgmd) is required; you most likely want to install the management client (ndb_mgm) as well. Both of these binaries also be found in the .tar.gz archive. Again, we assume that you have placed this archive in /var/tmp.

As system root, perform the following steps to install ndb_mgmd and ndb_mgm on the management node host:

  1. Change location to the /var/tmp directory, and extract the ndb_mgm and ndb_mgmd from the archive into a suitable directory such as /usr/local/bin:

    shell> cd /var/tmp
    shell> tar -zxvf mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64.tar.gz
    shell> cd mysql-cluster-gpl-8.0.22-linux-glibc2.12-x86_64
    shell> cp bin/ndb_mgm* /usr/local/bin
    

    (You can safely delete the directory created by unpacking the downloaded archive, and the files it contains, from /var/tmp once ndb_mgm and ndb_mgmd have been copied to the executables directory.)

  2. Change location to the directory into which you copied the files, and then make both of them executable:

    shell> cd /usr/local/bin
    shell> chmod +x ndb_mgm*
    

In Section 23.2.3, “Initial Configuration of NDB Cluster”, we create configuration files for all of the nodes in our example NDB Cluster.

23.2.1.2 Installing NDB Cluster from RPM

This section covers the steps necessary to install the correct executables for each type of NDB Cluster 8.0 node using RPM packages supplied by Oracle. For information about RPMs for previous versions of NDB Cluster, see Installation using old-style RPMs (NDB 7.5.3 and earlier).

As an alternative to the method described in this section, Oracle provides MySQL Repositories for NDB Cluster that are compatible with many common Linux distributions. Two repostories, listed here, are available for RPM-based distributions:

RPMs are available for both 32-bit and 64-bit Linux platforms. The filenames for these RPMs use the following pattern:

mysql-cluster-community-data-node-8.0.22-1.el7.x86_64.rpm

mysql-cluster-license-component-ver-rev.distro.arch.rpm

    license:= {commercial | community}

    component: {management-server | data-node | server | client | other—see text}

    ver: major.minor.release

    rev: major[.minor]

    distro: {el6 | el7 | sles12}

    arch: {i686 | x86_64}

license indicates whether the RPM is part of a Commercial or Community release of NDB Cluster. In the remainder of this section, we assume for the examples that you are installing a Community release.

Possible values for component, with descriptions, can be found in the following table:

Table 23.6 Components of the NDB Cluster RPM distribution

Component Description
auto-installer (DEPRECATED) NDB Cluster Auto Installer program; see Section 23.2.8, “The NDB Cluster Auto-Installer (No longer supported)”, for usage
client MySQL and NDB client programs; includes mysql client, ndb_mgm client, and other client tools
common Character set and error message information needed by the MySQL server
data-node ndbd and ndbmtd data node binaries
devel Headers and library files needed for MySQL client development
embedded Embedded MySQL server
embedded-compat Backwards-compatible embedded MySQL server
embedded-devel Header and library files for developing applications for embedded MySQL
java JAR files needed for support of ClusterJ applications
libs MySQL client libraries
libs-compat Backwards-compatible MySQL client libraries
management-server The NDB Cluster management server (ndb_mgmd)
memcached Files needed to support ndbmemcache
minimal-debuginfo Debug information for package server-minimal; useful when developing applications that use this package or when debugging this package
ndbclient NDB client library for running NDB API and MGM API applications (libndbclient)
ndbclient-devel Header and other files needed for developing NDB API and MGM API applications
nodejs Files needed to set up Node.JS support for NDB Cluster
server The MySQL server (mysqld) with NDB storage engine support included, and associated MySQL server programs
server-minimal Minimal installation of the MySQL server for NDB and related tools
test mysqltest, other MySQL test programs, and support files


A single bundle (.tar file) of all NDB Cluster RPMs for a given platform and architecture is also available. The name of this file follows the pattern shown here:

mysql-cluster-license-ver-rev.distro.arch.rpm-bundle.tar

You can extract the individual RPM files from this file using tar or your preferred tool for extracting archives.

The components required to install the three major types of NDB Cluster nodes are given in the following list:

  • Management node: management-server

  • Data node: data-node

  • SQL node: server and common

In addition, the client RPM should be installed to provide the ndb_mgm management client on at least one management node. You may also wish to install it on SQL nodes, to have mysql and other MySQL client programs available on these. We discuss installation of nodes by type later in this section.

ver represents the three-part NDB storage engine version number in 8.0.x format, shown as 8.0.22 in the examples. rev provides the RPM revision number in major.minor format. In the examples shown in this section, we use 1.1 for this value.

The distro (Linux distribution) is one of rhel5 (Oracle Linux 5, Red Hat Enterprise Linux 4 and 5), el6 (Oracle Linux 6, Red Hat Enterprise Linux 6), el7 (Oracle Linux 7, Red Hat Enterprise Linux 7), or sles12 (SUSE Enterprise Linux 12). For the examples in this section, we assume that the host runs Oracle Linux 7, Red Hat Enterprise Linux 7, or the equivalent (el7).

arch is i686 for 32-bit RPMs and x86_64 for 64-bit versions. In the examples shown here, we assume a 64-bit platform.

The NDB Cluster version number in the RPM file names (shown here as 8.0.22) can vary according to the version which you are actually using. It is very important that all of the Cluster RPMs to be installed have the same version number. The architecture should also be appropriate to the machine on which the RPM is to be installed; in particular, you should keep in mind that 64-bit RPMs (x86_64) cannot be used with 32-bit operating systems (use i686 for the latter).

Data nodes.  On a computer that is to host an NDB Cluster data node it is necessary to install only the data-node RPM. To do so, copy this RPM to the data node host, and run the following command as the system root user, replacing the name shown for the RPM as necessary to match that of the RPM downloaded from the MySQL website:

shell> rpm -Uhv mysql-cluster-community-data-node-8.0.22-1.el7.x86_64.rpm

This installs the ndbd and ndbmtd data node binaries in /usr/sbin. Either of these can be used to run a data node process on this host.

SQL nodes.  Copy the server and common RPMs to each machine to be used for hosting an NDB Cluster SQL node (server requires common). Install the server RPM by executing the following command as the system root user, replacing the name shown for the RPM as necessary to match the name of the RPM downloaded from the MySQL website:

shell> rpm -Uhv mysql-cluster-community-server-8.0.22-1.el7.x86_64.rpm

This installs the MySQL server binary (mysqld), with NDB storage engine support, in the /usr/sbin directory. It also installs all needed MySQL Server support files and useful MySQL server programs, including the mysql.server and mysqld_safe startup scripts (in /usr/share/mysql and /usr/bin, respectively). The RPM installer should take care of general configuration issues (such as creating the mysql user and group, if needed) automatically.

Important

You must use the versions of these RPMs released for NDB Cluster ; those released for the standard MySQL server do not provide support for the NDB storage engine.

To administer the SQL node (MySQL server), you should also install the client RPM, as shown here:

shell> rpm -Uhv mysql-cluster-community-client-8.0.22-1.el7.x86_64.rpm

This installs the mysql client and other MySQL client programs, such as mysqladmin and mysqldump, to /usr/bin.

Management nodes.  To install the NDB Cluster management server, it is necessary only to use the management-server RPM. Copy this RPM to the computer intended to host the management node, and then install it by running the following command as the system root user (replace the name shown for the RPM as necessary to match that of the management-server RPM downloaded from the MySQL website):

shell> rpm -Uhv mysql-cluster-community-management-server-8.0.22-1.el7.x86_64.rpm

This RPM installs the management server binary ndb_mgmd in the /usr/sbin directory. While this is the only program actually required for running a management node, it is also a good idea to have the ndb_mgm NDB Cluster management client available as well. You can obtain this program, as well as other NDB client programs such as ndb_desc and ndb_config, by installing the client RPM as described previously.

See Section 2.5.4, “Installing MySQL on Linux Using RPM Packages from Oracle”, for general information about installing MySQL using RPMs supplied by Oracle.

After installing from RPM, you still need to configure the cluster; see Section 23.2.3, “Initial Configuration of NDB Cluster”, for the relevant information.

It is very important that all of the Cluster RPMs to be installed have the same version number. The architecture designation should also be appropriate to the machine on which the RPM is to be installed; in particular, you should keep in mind that 64-bit RPMs cannot be used with 32-bit operating systems.

Data nodes.  On a computer that is to host a cluster data node it is necessary to install only the server RPM. To do so, copy this RPM to the data node host, and run the following command as the system root user, replacing the name shown for the RPM as necessary to match that of the RPM downloaded from the MySQL website:

shell> rpm -Uhv MySQL-Cluster-server-gpl-8.0.22-1.sles11.i386.rpm

Although this installs all NDB Cluster binaries, only the program ndbd or ndbmtd (both in /usr/sbin) is actually needed to run an NDB Cluster data node.

SQL nodes.  On each machine to be used for hosting a cluster SQL node, install the server RPM by executing the following command as the system root user, replacing the name shown for the RPM as necessary to match the name of the RPM downloaded from the MySQL website:

shell> rpm -Uhv MySQL-Cluster-server-gpl-8.0.22-1.sles11.i386.rpm

This installs the MySQL server binary (mysqld) with NDB storage engine support in the /usr/sbin directory, as well as all needed MySQL Server support files. It also installs the mysql.server and mysqld_safe startup scripts (in /usr/share/mysql and /usr/bin, respectively). The RPM installer should take care of general configuration issues (such as creating the mysql user and group, if needed) automatically.

To administer the SQL node (MySQL server), you should also install the client RPM, as shown here:

shell> rpm -Uhv MySQL-Cluster-client-gpl-8.0.22-1.sles11.i386.rpm

This installs the mysql client program.

Management nodes.  To install the NDB Cluster management server, it is necessary only to use the server RPM. Copy this RPM to the computer intended to host the management node, and then install it by running the following command as the system root user (replace the name shown for the RPM as necessary to match that of the server RPM downloaded from the MySQL website):

shell> rpm -Uhv MySQL-Cluster-server-gpl-8.0.22-1.sles11.i386.rpm

Although this RPM installs many other files, only the management server binary ndb_mgmd (in the /usr/sbin directory) is actually required for running a management node. The server RPM also installs ndb_mgm, the NDB management client.

See Section 2.5.4, “Installing MySQL on Linux Using RPM Packages from Oracle”, for general information about installing MySQL using RPMs supplied by Oracle. See Section 23.2.3, “Initial Configuration of NDB Cluster”, for information about required post-installation configuration.

23.2.1.3 Installing NDB Cluster Using .deb Files

The section provides information about installing NDB Cluster on Debian and related Linux distributions such Ubuntu using the .deb files supplied by Oracle for this purpose.

Oracle also provides an NDB Cluster APT repository for Debian and other distributions. See Installing MySQL NDB Cluster Using the APT Repository, for instructions and additional information.

Oracle provides .deb installer files for NDB Cluster for 32-bit and 64-bit platforms. For a Debian-based system, only a single installer file is necessary. This file is named using the pattern shown here, according to the applicable NDB Cluster version, Debian version, and architecture:

mysql-cluster-gpl-ndbver-debiandebianver-arch.deb

Here, ndbver is the 3-part NDB engine version number, debianver is the major version of Debian (8 or 9), and arch is one of i686 or x86_64. In the examples that follow, we assume you wish to install NDB 8.0.22 on a 64-bit Debian 9 system; in this case, the installer file is named mysql-cluster-gpl-8.0.22-debian9-x86_64.deb-bundle.tar.

Once you have downloaded the appropriate .deb file, you can untar it, and then install it from the command line using dpkg, like this:

shell> dpkg -i mysql-cluster-gpl-8.0.22-debian9-i686.deb

You can also remove it using dpkg as shown here:

shell> dpkg -r mysql

The installer file should also be compatible with most graphical package managers that work with .deb files, such as GDebi for the Gnome desktop.

The .deb file installs NDB Cluster under /opt/mysql/server-version/, where version is the 2-part release series version for the included MySQL server. For NDB 8.0, this is always 5.7. The directory layout is the same as that for the generic Linux binary distribution (see Table 2.3, “MySQL Installation Layout for Generic Unix/Linux Binary Package”), with the exception that startup scripts and configuration files are found in support-files instead of share. All NDB Cluster executables, such as ndb_mgm, ndbd, and ndb_mgmd, are placed in the bin directory.

23.2.1.4 Building NDB Cluster from Source on Linux

This section provides information about compiling NDB Cluster on Linux and other Unix-like platforms. Building NDB Cluster from source is similar to building the standard MySQL Server, although it differs in a few key respects discussed here. For general information about building MySQL from source, see Section 2.9, “Installing MySQL from Source”. For information about compiling NDB Cluster on Windows platforms, see Section 23.2.2.2, “Compiling and Installing NDB Cluster from Source on Windows”.

Building MySQL NDB Cluster 8.0 requires using the MySQL Server 8.0 sources. These are available from the MySQL downloads page at https://dev.mysql.com/downloads/. The archived source file should have a name similar to mysql-8.0.22.tar.gz. You can also obtain the sources from GitHub at https://github.com/mysql/mysql-server.

Note

In previous versions, building of NDB Cluster from standard MySQL Server sources was not supported. In MySQL 8.0 and NDB Cluster 8.0, this is no longer the case—both products are now built from the same sources.

The WITH_NDBCLUSTER option for CMake causes the binaries for the management nodes, data nodes, and other NDB Cluster programs to be built; it also causes mysqld to be compiled with NDB storage engine support. This option (or one of its aliases WITH_NDBCLUSTER_STORAGE_ENGINE and WITH_PLUGIN_NDBCLUSTER) is required when building NDB Cluster.

Important

The WITH_NDB_JAVA option is enabled by default. This means that, by default, if CMake cannot find the location of Java on your system, the configuration process fails; if you do not wish to enable Java and ClusterJ support, you must indicate this explicitly by configuring the build using -DWITH_NDB_JAVA=OFF. Use WITH_CLASSPATH to provide the Java classpath if needed.

For more information about CMake options specific to building NDB Cluster, see Options for Compiling NDB Cluster.

After you have run make && make install (or your system's equivalent), the result is similar to what is obtained by unpacking a precompiled binary to the same location.

Management nodes.  When building from source and running the default make install, the management server and management client binaries (ndb_mgmd and ndb_mgm) can be found in /usr/local/mysql/bin. Only ndb_mgmd is required to be present on a management node host; however, it is also a good idea to have ndb_mgm present on the same host machine. Neither of these executables requires a specific location on the host machine's file system.

Data nodes.  The only executable required on a data node host is the data node binary ndbd or ndbmtd. (mysqld, for example, does not have to be present on the host machine.) By default, when building from source, this file is placed in the directory /usr/local/mysql/bin. For installing on multiple data node hosts, only ndbd or ndbmtd need be copied to the other host machine or machines. (This assumes that all data node hosts use the same architecture and operating system; otherwise you may need to compile separately for each different platform.) The data node binary need not be in any particular location on the host's file system, as long as the location is known.

When compiling NDB Cluster from source, no special options are required for building multithreaded data node binaries. Configuring the build with NDB storage engine support causes ndbmtd to be built automatically; make install places the ndbmtd binary in the installation bin directory along with mysqld, ndbd, and ndb_mgm.

SQL nodes.  If you compile MySQL with clustering support, and perform the default installation (using make install as the system root user), mysqld is placed in /usr/local/mysql/bin. Follow the steps given in Section 2.9, “Installing MySQL from Source” to make mysqld ready for use. If you want to run multiple SQL nodes, you can use a copy of the same mysqld executable and its associated support files on several machines. The easiest way to do this is to copy the entire /usr/local/mysql directory and all directories and files contained within it to the other SQL node host or hosts, then repeat the steps from Section 2.9, “Installing MySQL from Source” on each machine. If you configure the build with a nondefault PREFIX option, you must adjust the directory accordingly.

In Section 23.2.3, “Initial Configuration of NDB Cluster”, we create configuration files for all of the nodes in our example NDB Cluster.

23.2.2 Installing NDB Cluster on Windows

This section describes installation procedures for NDB Cluster on Windows hosts. NDB Cluster 8.0 binaries for Windows can be obtained from https://dev.mysql.com/downloads/cluster/. For information about installing NDB Cluster on Windows from a binary release provided by Oracle, see Section 23.2.2.1, “Installing NDB Cluster on Windows from a Binary Release”.

It is also possible to compile and install NDB Cluster from source on Windows using Microsoft Visual Studio. For more information, see Section 23.2.2.2, “Compiling and Installing NDB Cluster from Source on Windows”.

23.2.2.1 Installing NDB Cluster on Windows from a Binary Release

This section describes a basic installation of NDB Cluster on Windows using a binary no-install NDB Cluster release provided by Oracle, using the same 4-node setup outlined in the beginning of this section (see Section 23.2, “NDB Cluster Installation”), as shown in the following table:

Table 23.7 Network addresses of nodes in example cluster

Node IP Address
Management node (mgmd) 198.51.100.10
SQL node (mysqld) 198.51.100.20
Data node "A" (ndbd) 198.51.100.30
Data node "B" (ndbd) 198.51.100.40

As on other platforms, the NDB Cluster host computer running an SQL node must have installed on it a MySQL Server binary (mysqld.exe). You should also have the MySQL client (mysql.exe) on this host. For management nodes and data nodes, it is not necessary to install the MySQL Server binary; however, each management node requires the management server daemon (ndb_mgmd.exe); each data node requires the data node daemon (ndbd.exe or ndbmtd.exe). For this example, we refer to ndbd.exe as the data node executable, but you can install ndbmtd.exe, the multithreaded version of this program, instead, in exactly the same way. You should also install the management client (ndb_mgm.exe) on the management server host. This section covers the steps necessary to install the correct Windows binaries for each type of NDB Cluster node.

Note

As with other Windows programs, NDB Cluster executables are named with the .exe file extension. However, it is not necessary to include the .exe extension when invoking these programs from the command line. Therefore, we often simply refer to these programs in this documentation as mysqld, mysql, ndb_mgmd, and so on. You should understand that, whether we refer (for example) to mysqld or mysqld.exe, either name means the same thing (the MySQL Server program).

For setting up an NDB Cluster using Oracles's no-install binaries, the first step in the installation process is to download the latest NDB Cluster Windows ZIP binary archive from https://dev.mysql.com/downloads/cluster/. This archive has a filename of the mysql-cluster-gpl-ver-winarch.zip, where ver is the NDB storage engine version (such as 8.0.22), and arch is the architecture (32 for 32-bit binaries, and 64 for 64-bit binaries). For example, the NDB Cluster 8.0.22 archive for 64-bit Windows systems is named mysql-cluster-gpl-8.0.22-win64.zip.

You can run 32-bit NDB Cluster binaries on both 32-bit and 64-bit versions of Windows; however, 64-bit NDB Cluster binaries can be used only on 64-bit versions of Windows. If you are using a 32-bit version of Windows on a computer that has a 64-bit CPU, then you must use the 32-bit NDB Cluster binaries.

To minimize the number of files that need to be downloaded from the Internet or copied between machines, we start with the computer where you intend to run the SQL node.

SQL node.  We assume that you have placed a copy of the archive in the directory C:\Documents and Settings\username\My Documents\Downloads on the computer having the IP address 198.51.100.20, where username is the name of the current user. (You can obtain this name using ECHO %USERNAME% on the command line.) To install and run NDB Cluster executables as Windows services, this user should be a member of the Administrators group.

Extract all the files from the archive. The Extraction Wizard integrated with Windows Explorer is adequate for this task. (If you use a different archive program, be sure that it extracts all files and directories from the archive, and that it preserves the archive's directory structure.) When you are asked for a destination directory, enter C:\, which causes the Extraction Wizard to extract the archive to the directory C:\mysql-cluster-gpl-ver-winarch. Rename this directory to C:\mysql.

It is possible to install the NDB Cluster binaries to directories other than C:\mysql\bin; however, if you do so, you must modify the paths shown in this procedure accordingly. In particular, if the MySQL Server (SQL node) binary is installed to a location other than C:\mysql or C:\Program Files\MySQL\MySQL Server 8.0, or if the SQL node's data directory is in a location other than C:\mysql\data or C:\Program Files\MySQL\MySQL Server 8.0\data, extra configuration options must be used on the command line or added to the my.ini or my.cnf file when starting the SQL node. For more information about configuring a MySQL Server to run in a nonstandard location, see Section 2.3.4, “Installing MySQL on Microsoft Windows Using a noinstall ZIP Archive”.

For a MySQL Server with NDB Cluster support to run as part of an NDB Cluster, it must be started with the options --ndbcluster and --ndb-connectstring. While you can specify these options on the command line, it is usually more convenient to place them in an option file. To do this, create a new text file in Notepad or another text editor. Enter the following configuration information into this file:

[mysqld]
# Options for mysqld process:
ndbcluster                       # run NDB storage engine
ndb-connectstring=198.51.100.10  # location of management server

You can add other options used by this MySQL Server if desired (see Section 2.3.4.2, “Creating an Option File”), but the file must contain the options shown, at a minimum. Save this file as C:\mysql\my.ini. This completes the installation and setup for the SQL node.

Data nodes.  An NDB Cluster data node on a Windows host requires only a single executable, one of either ndbd.exe or ndbmtd.exe. For this example, we assume that you are using ndbd.exe, but the same instructions apply when using ndbmtd.exe. On each computer where you wish to run a data node (the computers having the IP addresses 198.51.100.30 and 198.51.100.40), create the directories C:\mysql, C:\mysql\bin, and C:\mysql\cluster-data; then, on the computer where you downloaded and extracted the no-install archive, locate ndbd.exe in the C:\mysql\bin directory. Copy this file to the C:\mysql\bin directory on each of the two data node hosts.

To function as part of an NDB Cluster, each data node must be given the address or hostname of the management server. You can supply this information on the command line using the --ndb-connectstring or -c option when starting each data node process. However, it is usually preferable to put this information in an option file. To do this, create a new text file in Notepad or another text editor and enter the following text:

[mysql_cluster]
# Options for data node process:
ndb-connectstring=198.51.100.10  # location of management server

Save this file as C:\mysql\my.ini on the data node host. Create another text file containing the same information and save it on as C:mysql\my.ini on the other data node host, or copy the my.ini file from the first data node host to the second one, making sure to place the copy in the second data node's C:\mysql directory. Both data node hosts are now ready to be used in the NDB Cluster, which leaves only the management node to be installed and configured.

Management node.  The only executable program required on a computer used for hosting an NDB Cluster management node is the management server program ndb_mgmd.exe. However, in order to administer the NDB Cluster once it has been started, you should also install the NDB Cluster management client program ndb_mgm.exe on the same machine as the management server. Locate these two programs on the machine where you downloaded and extracted the no-install archive; this should be the directory C:\mysql\bin on the SQL node host. Create the directory C:\mysql\bin on the computer having the IP address 198.51.100.10, then copy both programs to this directory.

You should now create two configuration files for use by ndb_mgmd.exe:

  1. A local configuration file to supply configuration data specific to the management node itself. Typically, this file needs only to supply the location of the NDB Cluster global configuration file (see item 2).

    To create this file, start a new text file in Notepad or another text editor, and enter the following information:

    [mysql_cluster]
    # Options for management node process
    config-file=C:/mysql/bin/config.ini
    

    Save this file as the text file C:\mysql\bin\my.ini.

  2. A global configuration file from which the management node can obtain configuration information governing the NDB Cluster as a whole. At a minimum, this file must contain a section for each node in the NDB Cluster, and the IP addresses or hostnames for the management node and all data nodes (HostName configuration parameter). It is also advisable to include the following additional information:

    Create a new text file using a text editor such as Notepad, and input the following information:

    [ndbd default]
    # Options affecting ndbd processes on all data nodes:
    NoOfReplicas=2                      # Number of fragment replicas
    DataDir=C:/mysql/cluster-data       # Directory for each data node's data files
                                        # Forward slashes used in directory path,
                                        # rather than backslashes. This is correct;
                                        # see Important note in text
    DataMemory=80M    # Memory allocated to data storage
    IndexMemory=18M   # Memory allocated to index storage
                      # For DataMemory and IndexMemory, we have used the
                      # default values. Since the "world" database takes up
                      # only about 500KB, this should be more than enough for
                      # this example Cluster setup.
    
    [ndb_mgmd]
    # Management process options:
    HostName=198.51.100.10              # Hostname or IP address of management node
    DataDir=C:/mysql/bin/cluster-logs   # Directory for management node log files
    
    [ndbd]
    # Options for data node "A":
                                    # (one [ndbd] section per data node)
    HostName=198.51.100.30          # Hostname or IP address
    
    [ndbd]
    # Options for data node "B":
    HostName=198.51.100.40          # Hostname or IP address
    
    [mysqld]
    # SQL node options:
    HostName=198.51.100.20          # Hostname or IP address
    

    Save this file as the text file C:\mysql\bin\config.ini.

Important

A single backslash character (\) cannot be used when specifying directory paths in program options or configuration files used by NDB Cluster on Windows. Instead, you must either escape each backslash character with a second backslash (\\), or replace the backslash with a forward slash character (/). For example, the following line from the [ndb_mgmd] section of an NDB Cluster config.ini file does not work:

DataDir=C:\mysql\bin\cluster-logs

Instead, you may use either of the following:

DataDir=C:\\mysql\\bin\\cluster-logs  # Escaped backslashes
DataDir=C:/mysql/bin/cluster-logs     # Forward slashes

For reasons of brevity and legibility, we recommend that you use forward slashes in directory paths used in NDB Cluster program options and configuration files on Windows.

23.2.2.2 Compiling and Installing NDB Cluster from Source on Windows

Oracle provides precompiled NDB Cluster binaries for Windows which should be adequate for most users. However, if you wish, it is also possible to compile NDB Cluster for Windows from source code. The procedure for doing this is almost identical to the procedure used to compile the standard MySQL Server binaries for Windows, and uses the same tools. However, there are two major differences:

  • Building MySQL NDB Cluster 8.0 requires using the MySQL Server 8.0 sources. These are available from the MySQL downloads page at https://dev.mysql.com/downloads/. The archived source file should have a name similar to mysql-8.0.22.tar.gz. You can also obtain the sources from GitHub at https://github.com/mysql/mysql-server.

  • You must configure the build using the WITH_NDBCLUSTER option in addition to any other build options you wish to use with CMake. WITH_NDBCLUSTER_STORAGE_ENGINE and WITH_PLUGIN_NDBCLUSTER are supported as aliases for WITH_NDBCLUSTER, and work in exactly the same way.

Important

The WITH_NDB_JAVA option is enabled by default. This means that, by default, if CMake cannot find the location of Java on your system, the configuration process fails; if you do not wish to enable Java and ClusterJ support, you must indicate this explicitly by configuring the build using -DWITH_NDB_JAVA=OFF. (Bug #12379735) Use WITH_CLASSPATH to provide the Java classpath if needed.

For more information about CMake options specific to building NDB Cluster, see Options for Compiling NDB Cluster.

Once the build process is complete, you can create a Zip archive containing the compiled binaries; Section 2.9.4, “Installing MySQL Using a Standard Source Distribution” provides the commands needed to perform this task on Windows systems. The NDB Cluster binaries can be found in the bin directory of the resulting archive, which is equivalent to the no-install archive, and which can be installed and configured in the same manner. For more information, see Section 23.2.2.1, “Installing NDB Cluster on Windows from a Binary Release”.

23.2.2.3 Initial Startup of NDB Cluster on Windows

Once the NDB Cluster executables and needed configuration files are in place, performing an initial start of the cluster is simply a matter of starting the NDB Cluster executables for all nodes in the cluster. Each cluster node process must be started separately, and on the host computer where it resides. The management node should be started first, followed by the data nodes, and then finally by any SQL nodes.

  1. On the management node host, issue the following command from the command line to start the management node process. The output should appear similar to what is shown here:

    C:\mysql\bin> ndb_mgmd
    2010-06-23 07:53:34 [MgmtSrvr] INFO -- NDB Cluster Management Server. mysql-8.0.23-ndb-8.0.23
    2010-06-23 07:53:34 [MgmtSrvr] INFO -- Reading cluster configuration from 'config.ini'
    

    The management node process continues to print logging output to the console. This is normal, because the management node is not running as a Windows service. (If you have used NDB Cluster on a Unix-like platform such as Linux, you may notice that the management node's default behavior in this regard on Windows is effectively the opposite of its behavior on Unix systems, where it runs by default as a Unix daemon process. This behavior is also true of NDB Cluster data node processes running on Windows.) For this reason, do not close the window in which ndb_mgmd.exe is running; doing so kills the management node process. (See Section 23.2.2.4, “Installing NDB Cluster Processes as Windows Services”, where we show how to install and run NDB Cluster processes as Windows services.)

    The required -f option tells the management node where to find the global configuration file (config.ini). The long form of this option is --config-file.

    Important

    An NDB Cluster management node caches the configuration data that it reads from config.ini; once it has created a configuration cache, it ignores the config.ini file on subsequent starts unless forced to do otherwise. This means that, if the management node fails to start due to an error in this file, you must make the management node re-read config.ini after you have corrected any errors in it. You can do this by starting ndb_mgmd.exe with the --reload or --initial option on the command line. Either of these options works to refresh the configuration cache.

    It is not necessary or advisable to use either of these options in the management node's my.ini file.

    For additional information about options which can be used with ndb_mgmd, see Section 23.4.4, “ndb_mgmd — The NDB Cluster Management Server Daemon”, as well as Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

  2. On each of the data node hosts, run the command shown here to start the data node processes:

    C:\mysql\bin> ndbd
    2010-06-23 07:53:46 [ndbd] INFO -- Configuration fetched from 'localhost:1186', generation: 1
    

    In each case, the first line of output from the data node process should resemble what is shown in the preceding example, and is followed by additional lines of logging output. As with the management node process, this is normal, because the data node is not running as a Windows service. For this reason, do not close the console window in which the data node process is running; doing so kills ndbd.exe. (For more information, see Section 23.2.2.4, “Installing NDB Cluster Processes as Windows Services”.)

  3. Do not start the SQL node yet; it cannot connect to the cluster until the data nodes have finished starting, which may take some time. Instead, in a new console window on the management node host, start the NDB Cluster management client ndb_mgm.exe, which should be in C:\mysql\bin on the management node host. (Do not try to re-use the console window where ndb_mgmd.exe is running by typing CTRL+C, as this kills the management node.) The resulting output should look like this:

    C:\mysql\bin> ndb_mgm
    -- NDB Cluster -- Management Client --
    ndb_mgm>
    

    When the prompt ndb_mgm> appears, this indicates that the management client is ready to receive NDB Cluster management commands. You can observe the status of the data nodes as they start by entering ALL STATUS at the management client prompt. This command causes a running report of the data nodes's startup sequence, which should look something like this:

    ndb_mgm> ALL STATUS
    Connected to Management Server at: localhost:1186
    Node 2: starting (Last completed phase 3) (mysql-8.0.23-ndb-8.0.23)
    Node 3: starting (Last completed phase 3) (mysql-8.0.23-ndb-8.0.23)
    
    Node 2: starting (Last completed phase 4) (mysql-8.0.23-ndb-8.0.23)
    Node 3: starting (Last completed phase 4) (mysql-8.0.23-ndb-8.0.23)
    
    Node 2: Started (version 8.0.23)
    Node 3: Started (version 8.0.23)
    
    ndb_mgm>
    
    Note

    Commands issued in the management client are not case-sensitive; we use uppercase as the canonical form of these commands, but you are not required to observe this convention when inputting them into the ndb_mgm client. For more information, see Section 23.5.1, “Commands in the NDB Cluster Management Client”.

    The output produced by ALL STATUS is likely to vary from what is shown here, according to the speed at which the data nodes are able to start, the release version number of the NDB Cluster software you are using, and other factors. What is significant is that, when you see that both data nodes have started, you are ready to start the SQL node.

    You can leave ndb_mgm.exe running; it has no negative impact on the performance of the NDB Cluster, and we use it in the next step to verify that the SQL node is connected to the cluster after you have started it.

  4. On the computer designated as the SQL node host, open a console window and navigate to the directory where you unpacked the NDB Cluster binaries (if you are following our example, this is C:\mysql\bin).

    Start the SQL node by invoking mysqld.exe from the command line, as shown here:

    C:\mysql\bin> mysqld --console
    

    The --console option causes logging information to be written to the console, which can be helpful in the event of problems. (Once you are satisfied that the SQL node is running in a satisfactory manner, you can stop it and restart it out without the --console option, so that logging is performed normally.)

    In the console window where the management client (ndb_mgm.exe) is running on the management node host, enter the SHOW command, which should produce output similar to what is shown here:

    ndb_mgm> SHOW
    Connected to Management Server at: localhost:1186
    Cluster Configuration
    ---------------------
    [ndbd(NDB)]     2 node(s)
    id=2    @198.51.100.30  (Version: 8.0.23-ndb-8.0.23, Nodegroup: 0, *)
    id=3    @198.51.100.40  (Version: 8.0.23-ndb-8.0.23, Nodegroup: 0)
    
    [ndb_mgmd(MGM)] 1 node(s)
    id=1    @198.51.100.10  (Version: 8.0.23-ndb-8.0.23)
    
    [mysqld(API)]   1 node(s)
    id=4    @198.51.100.20  (Version: 8.0.23-ndb-8.0.23)
    

    You can also verify that the SQL node is connected to the NDB Cluster in the mysql client (mysql.exe) using the SHOW ENGINE NDB STATUS statement.

You should now be ready to work with database objects and data using NDB Cluster 's NDBCLUSTER storage engine. See Section 23.2.5, “NDB Cluster Example with Tables and Data”, for more information and examples.

You can also install ndb_mgmd.exe, ndbd.exe, and ndbmtd.exe as Windows services. For information on how to do this, see Section 23.2.2.4, “Installing NDB Cluster Processes as Windows Services”).

23.2.2.4 Installing NDB Cluster Processes as Windows Services

Once you are satisfied that NDB Cluster is running as desired, you can install the management nodes and data nodes as Windows services, so that these processes are started and stopped automatically whenever Windows is started or stopped. This also makes it possible to control these processes from the command line with the appropriate SC START and SC STOP commands, or using the Windows graphical Services utility. NET START and NET STOP commands can also be used.

Installing programs as Windows services usually must be done using an account that has Administrator rights on the system.

To install the management node as a service on Windows, invoke ndb_mgmd.exe from the command line on the machine hosting the management node, using the --install option, as shown here:

C:\> C:\mysql\bin\ndb_mgmd.exe --install
Installing service 'NDB Cluster Management Server'
  as '"C:\mysql\bin\ndbd.exe" "--service=ndb_mgmd"'
Service successfully installed.
Important

When installing an NDB Cluster program as a Windows service, you should always specify the complete path; otherwise the service installation may fail with the error The system cannot find the file specified.

The --install option must be used first, ahead of any other options that might be specified for ndb_mgmd.exe. However, it is preferable to specify such options in an options file instead. If your options file is not in one of the default locations as shown in the output of ndb_mgmd.exe --help, you can specify the location using the --config-file option.

Now you should be able to start and stop the management server like this:

C:\> SC START ndb_mgmd

C:\> SC STOP ndb_mgmd
Note

If using NET commands, you can also start or stop the management server as a Windows service using the descriptive name, as shown here:

C:\> NET START 'NDB Cluster Management Server'
The NDB Cluster Management Server service is starting.
The NDB Cluster Management Server service was started successfully.

C:\> NET STOP  'NDB Cluster Management Server'
The NDB Cluster Management Server service is stopping..
The NDB Cluster Management Server service was stopped successfully.

It is usually simpler to specify a short service name or to permit the default service name to be used when installing the service, and then reference that name when starting or stopping the service. To specify a service name other than ndb_mgmd, append it to the --install option, as shown in this example:

C:\> C:\mysql\bin\ndb_mgmd.exe --install=mgmd1
Installing service 'NDB Cluster Management Server'
  as '"C:\mysql\bin\ndb_mgmd.exe" "--service=mgmd1"'
Service successfully installed.

Now you should be able to start or stop the service using the name you have specified, like this:

C:\> SC START mgmd1

C:\> SC STOP mgmd1

To remove the management node service, use SC DELETE service_name:

C:\> SC DELETE mgmd1

Alternatively, invoke ndb_mgmd.exe with the --remove option, as shown here:

C:\> C:\mysql\bin\ndb_mgmd.exe --remove
Removing service 'NDB Cluster Management Server'
Service successfully removed.

If you installed the service using a service name other than the default, pass the service name as the value of the ndb_mgmd.exe --remove option, like this:

C:\> C:\mysql\bin\ndb_mgmd.exe --remove=mgmd1
Removing service 'mgmd1'
Service successfully removed.

Installation of an NDB Cluster data node process as a Windows service can be done in a similar fashion, using the --install option for ndbd.exe (or ndbmtd.exe), as shown here:

C:\> C:\mysql\bin\ndbd.exe --install
Installing service 'NDB Cluster Data Node Daemon' as '"C:\mysql\bin\ndbd.exe" "--service=ndbd"'
Service successfully installed.

Now you can start or stop the data node as shown in the following example:

C:\> SC START ndbd

C:\> SC STOP ndbd

To remove the data node service, use SC DELETE service_name:

C:\> SC DELETE ndbd

Alternatively, invoke ndbd.exe with the --remove option, as shown here:

C:\> C:\mysql\bin\ndbd.exe --remove
Removing service 'NDB Cluster Data Node Daemon'
Service successfully removed.

As with ndb_mgmd.exe (and mysqld.exe), when installing ndbd.exe as a Windows service, you can also specify a name for the service as the value of --install, and then use it when starting or stopping the service, like this:

C:\> C:\mysql\bin\ndbd.exe --install=dnode1
Installing service 'dnode1' as '"C:\mysql\bin\ndbd.exe" "--service=dnode1"'
Service successfully installed.

C:\> SC START dnode1

C:\> SC STOP dnode1

If you specified a service name when installing the data node service, you can use this name when removing it as well, as shown here:

C:\> SC DELETE dnode1

Alternatively, you can pass the service name as the value of the ndbd.exe --remove option, as shown here:

C:\> C:\mysql\bin\ndbd.exe --remove=dnode1
Removing service 'dnode1'
Service successfully removed.

Installation of the SQL node as a Windows service, starting the service, stopping the service, and removing the service are done in a similar fashion, using mysqld --install, SC START, SC STOP, and SC DELETE (or mysqld --remove). NET commands can also be used to start or stop a service. For additional information, see Section 2.3.4.8, “Starting MySQL as a Windows Service”.

23.2.3 Initial Configuration of NDB Cluster

In this section, we discuss manual configuration of an installed NDB Cluster by creating and editing configuration files.

NDB Cluster also provides a GUI installer which can be used to perform the configuration without the need to edit text files in a separate application. For more information, see Section 23.2.8, “The NDB Cluster Auto-Installer (No longer supported)”.

For our four-node, four-host NDB Cluster (see Cluster nodes and host computers), it is necessary to write four configuration files, one per node host.

  • Each data node or SQL node requires a my.cnf file that provides two pieces of information: a connection string that tells the node where to find the management node, and a line telling the MySQL server on this host (the machine hosting the data node) to enable the NDBCLUSTER storage engine.

    For more information on connection strings, see Section 23.3.3.3, “NDB Cluster Connection Strings”.

  • The management node needs a config.ini file telling it how many fragment replicas to maintain, how much memory to allocate for data and indexes on each data node, where to find the data nodes, where to save data to disk on each data node, and where to find any SQL nodes.

Configuring the data nodes and SQL nodes.  The my.cnf file needed for the data nodes is fairly simple. The configuration file should be located in the /etc directory and can be edited using any text editor. (Create the file if it does not exist.) For example:

shell> vi /etc/my.cnf
Note

We show vi being used here to create the file, but any text editor should work just as well.

For each data node and SQL node in our example setup, my.cnf should look like this:

[mysqld]
# Options for mysqld process:
ndbcluster                      # run NDB storage engine

[mysql_cluster]
# Options for NDB Cluster processes:
ndb-connectstring=198.51.100.10  # location of management server

After entering the preceding information, save this file and exit the text editor. Do this for the machines hosting data node A, data node B, and the SQL node.

Important

Once you have started a mysqld process with the ndbcluster and ndb-connectstring parameters in the [mysqld] and [mysql_cluster] sections of the my.cnf file as shown previously, you cannot execute any CREATE TABLE or ALTER TABLE statements without having actually started the cluster. Otherwise, these statements fail with an error. This is by design.

Configuring the management node.  The first step in configuring the management node is to create the directory in which the configuration file can be found and then to create the file itself. For example (running as root):

shell> mkdir /var/lib/mysql-cluster
shell> cd /var/lib/mysql-cluster
shell> vi config.ini

For our representative setup, the config.ini file should read as follows:

[ndbd default]
# Options affecting ndbd processes on all data nodes:
NoOfReplicas=2    # Number of fragment replicas
DataMemory=98M    # How much memory to allocate for data storage

[ndb_mgmd]
# Management process options:
HostName=198.51.100.10          # Hostname or IP address of management node
DataDir=/var/lib/mysql-cluster  # Directory for management node log files

[ndbd]
# Options for data node "A":
                                # (one [ndbd] section per data node)
HostName=198.51.100.30          # Hostname or IP address
NodeId=2                        # Node ID for this data node
DataDir=/usr/local/mysql/data   # Directory for this data node's data files

[ndbd]
# Options for data node "B":
HostName=198.51.100.40          # Hostname or IP address
NodeId=3                        # Node ID for this data node
DataDir=/usr/local/mysql/data   # Directory for this data node's data files

[mysqld]
# SQL node options:
HostName=198.51.100.20          # Hostname or IP address
                                # (additional mysqld connections can be
                                # specified for this node for various
                                # purposes such as running ndb_restore)
Note

The world database can be downloaded from https://dev.mysql.com/doc/index-other.html.

After all the configuration files have been created and these minimal options have been specified, you are ready to proceed with starting the cluster and verifying that all processes are running. We discuss how this is done in Section 23.2.4, “Initial Startup of NDB Cluster”.

For more detailed information about the available NDB Cluster configuration parameters and their uses, see Section 23.3.3, “NDB Cluster Configuration Files”, and Section 23.3, “Configuration of NDB Cluster”. For configuration of NDB Cluster as relates to making backups, see Section 23.5.8.3, “Configuration for NDB Cluster Backups”.

Note

The default port for Cluster management nodes is 1186; the default port for data nodes is 2202. However, the cluster can automatically allocate ports for data nodes from those that are already free.

23.2.4 Initial Startup of NDB Cluster

Starting the cluster is not very difficult after it has been configured. Each cluster node process must be started separately, and on the host where it resides. The management node should be started first, followed by the data nodes, and then finally by any SQL nodes:

  1. On the management host, issue the following command from the system shell to start the management node process:

    shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini
    

    The first time that it is started, ndb_mgmd must be told where to find its configuration file, using the -f or --config-file option. (See Section 23.4.4, “ndb_mgmd — The NDB Cluster Management Server Daemon”, for details.)

    For additional options which can be used with ndb_mgmd, see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

  2. On each of the data node hosts, run this command to start the ndbd process:

    shell> ndbd
    
  3. If you used RPM files to install MySQL on the cluster host where the SQL node is to reside, you can (and should) use the supplied startup script to start the MySQL server process on the SQL node.

If all has gone well, and the cluster has been set up correctly, the cluster should now be operational. You can test this by invoking the ndb_mgm management node client. The output should look like that shown here, although you might see some slight differences in the output depending upon the exact version of MySQL that you are using:

shell> ndb_mgm
-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=2    @198.51.100.30  (Version: 8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=3    @198.51.100.40  (Version: 8.0.23-ndb-8.0.23, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=1    @198.51.100.10  (Version: 8.0.23-ndb-8.0.23)

[mysqld(API)]   1 node(s)
id=4    @198.51.100.20  (Version: 8.0.23-ndb-8.0.23)

The SQL node is referenced here as [mysqld(API)], which reflects the fact that the mysqld process is acting as an NDB Cluster API node.

Note

The IP address shown for a given NDB Cluster SQL or other API node in the output of SHOW is the address used by the SQL or API node to connect to the cluster data nodes, and not to any management node.

You should now be ready to work with databases, tables, and data in NDB Cluster. See Section 23.2.5, “NDB Cluster Example with Tables and Data”, for a brief discussion.

23.2.5 NDB Cluster Example with Tables and Data

Note

The information in this section applies to NDB Cluster running on both Unix and Windows platforms.

Working with database tables and data in NDB Cluster is not much different from doing so in standard MySQL. There are two key points to keep in mind:

  • For a table to be replicated in the cluster, it must use the NDBCLUSTER storage engine. To specify this, use the ENGINE=NDBCLUSTER or ENGINE=NDB option when creating the table:

    CREATE TABLE tbl_name (col_name column_definitions) ENGINE=NDBCLUSTER;
    

    Alternatively, for an existing table that uses a different storage engine, use ALTER TABLE to change the table to use NDBCLUSTER:

    ALTER TABLE tbl_name ENGINE=NDBCLUSTER;
    
  • Every NDBCLUSTER table has a primary key. If no primary key is defined by the user when a table is created, the NDBCLUSTER storage engine automatically generates a hidden one. Such a key takes up space just as does any other table index. (It is not uncommon to encounter problems due to insufficient memory for accommodating these automatically created indexes.)

If you are importing tables from an existing database using the output of mysqldump, you can open the SQL script in a text editor and add the ENGINE option to any table creation statements, or replace any existing ENGINE options. Suppose that you have the world sample database on another MySQL server that does not support NDB Cluster, and you want to export the City table:

shell> mysqldump --add-drop-table world City > city_table.sql

The resulting city_table.sql file contains this table creation statement (and the INSERT statements necessary to import the table data):

DROP TABLE IF EXISTS `City`;
CREATE TABLE `City` (
  `ID` int(11) NOT NULL auto_increment,
  `Name` char(35) NOT NULL default '',
  `CountryCode` char(3) NOT NULL default '',
  `District` char(20) NOT NULL default '',
  `Population` int(11) NOT NULL default '0',
  PRIMARY KEY  (`ID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
(remaining INSERT statements omitted)

You need to make sure that MySQL uses the NDBCLUSTER storage engine for this table. There are two ways that this can be accomplished. One of these is to modify the table definition before importing it into the Cluster database. Using the City table as an example, modify the ENGINE option of the definition as follows:

DROP TABLE IF EXISTS `City`;
CREATE TABLE `City` (
  `ID` int(11) NOT NULL auto_increment,
  `Name` char(35) NOT NULL default '',
  `CountryCode` char(3) NOT NULL default '',
  `District` char(20) NOT NULL default '',
  `Population` int(11) NOT NULL default '0',
  PRIMARY KEY  (`ID`)
) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;

INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
(remaining INSERT statements omitted)

This must be done for the definition of each table that is to be part of the clustered database. The easiest way to accomplish this is to do a search-and-replace on the file that contains the definitions and replace all instances of TYPE=engine_name or ENGINE=engine_name with ENGINE=NDBCLUSTER. If you do not want to modify the file, you can use the unmodified file to create the tables, and then use ALTER TABLE to change their storage engine. The particulars are given later in this section.

Assuming that you have already created a database named world on the SQL node of the cluster, you can then use the mysql command-line client to read city_table.sql, and create and populate the corresponding table in the usual manner:

shell> mysql world < city_table.sql

It is very important to keep in mind that the preceding command must be executed on the host where the SQL node is running (in this case, on the machine with the IP address 198.51.100.20).

To create a copy of the entire world database on the SQL node, use mysqldump on the noncluster server to export the database to a file named world.sql (for example, in the /tmp directory). Then modify the table definitions as just described and import the file into the SQL node of the cluster like this:

shell> mysql world < /tmp/world.sql

If you save the file to a different location, adjust the preceding instructions accordingly.

Running SELECT queries on the SQL node is no different from running them on any other instance of a MySQL server. To run queries from the command line, you first need to log in to the MySQL Monitor in the usual way (specify the root password at the Enter password: prompt):

shell> mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1 to server version: 8.0.23-ndb-8.0.23

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql>

We simply use the MySQL server's root account and assume that you have followed the standard security precautions for installing a MySQL server, including setting a strong root password. For more information, see Section 2.10.4, “Securing the Initial MySQL Account”.

It is worth taking into account that NDB Cluster nodes do not make use of the MySQL privilege system when accessing one another. Setting or changing MySQL user accounts (including the root account) effects only applications that access the SQL node, not interaction between nodes. See Section 23.5.17.2, “NDB Cluster and MySQL Privileges”, for more information.

If you did not modify the ENGINE clauses in the table definitions prior to importing the SQL script, you should run the following statements at this point:

mysql> USE world;
mysql> ALTER TABLE City ENGINE=NDBCLUSTER;
mysql> ALTER TABLE Country ENGINE=NDBCLUSTER;
mysql> ALTER TABLE CountryLanguage ENGINE=NDBCLUSTER;

Selecting a database and running a SELECT query against a table in that database is also accomplished in the usual manner, as is exiting the MySQL Monitor:

mysql> USE world;
mysql> SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5;
+-----------+------------+
| Name      | Population |
+-----------+------------+
| Bombay    |   10500000 |
| Seoul     |    9981619 |
| São Paulo |    9968485 |
| Shanghai  |    9696300 |
| Jakarta   |    9604900 |
+-----------+------------+
5 rows in set (0.34 sec)

mysql> \q
Bye

shell>

Applications that use MySQL can employ standard APIs to access NDB tables. It is important to remember that your application must access the SQL node, and not the management or data nodes. This brief example shows how we might execute the SELECT statement just shown by using the PHP 5.X mysqli extension running on a Web server elsewhere on the network:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
  "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
  <meta http-equiv="Content-Type"
           content="text/html; charset=iso-8859-1">
  <title>SIMPLE mysqli SELECT</title>
</head>
<body>
<?php
  # connect to SQL node:
  $link = new mysqli('198.51.100.20', 'root', 'root_password', 'world');
  # parameters for mysqli constructor are:
  #   host, user, password, database

  if( mysqli_connect_errno() )
    die("Connect failed: " . mysqli_connect_error());

  $query = "SELECT Name, Population
            FROM City
            ORDER BY Population DESC
            LIMIT 5";

  # if no errors...
  if( $result = $link->query($query) )
  {
?>
<table border="1" width="40%" cellpadding="4" cellspacing ="1">
  <tbody>
  <tr>
    <th width="10%">City</th>
    <th>Population</th>
  </tr>
<?
    # then display the results...
    while($row = $result->fetch_object())
      printf("<tr>\n  <td align=\"center\">%s</td><td>%d</td>\n</tr>\n",
              $row->Name, $row->Population);
?>
  </tbody
</table>
<?
  # ...and verify the number of rows that were retrieved
    printf("<p>Affected rows: %d</p>\n", $link->affected_rows);
  }
  else
    # otherwise, tell us what went wrong
    echo mysqli_error();

  # free the result set and the mysqli connection object
  $result->close();
  $link->close();
?>
</body>
</html>

We assume that the process running on the Web server can reach the IP address of the SQL node.

In a similar fashion, you can use the MySQL C API, Perl-DBI, Python-mysql, or MySQL Connectors to perform the tasks of data definition and manipulation just as you would normally with MySQL.

23.2.6 Safe Shutdown and Restart of NDB Cluster

To shut down the cluster, enter the following command in a shell on the machine hosting the management node:

shell> ndb_mgm -e shutdown

The -e option here is used to pass a command to the ndb_mgm client from the shell. (See Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”, for more information about this option.) The command causes the ndb_mgm, ndb_mgmd, and any ndbd or ndbmtd processes to terminate gracefully. Any SQL nodes can be terminated using mysqladmin shutdown and other means. On Windows platforms, assuming that you have installed the SQL node as a Windows service, you can use SC STOP service_name or NET STOP service_name.

To restart the cluster on Unix platforms, run these commands:

  • On the management host (198.51.100.10 in our example setup):

    shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini
    
  • On each of the data node hosts (198.51.100.30 and 198.51.100.40):

    shell> ndbd
    
  • Use the ndb_mgm client to verify that both data nodes have started successfully.

  • On the SQL host (198.51.100.20):

    shell> mysqld_safe &
    

On Windows platforms, assuming that you have installed all NDB Cluster processes as Windows services using the default service names (see Section 23.2.2.4, “Installing NDB Cluster Processes as Windows Services”), you can restart the cluster as follows:

  • On the management host (198.51.100.10 in our example setup), execute the following command:

    C:\> SC START ndb_mgmd
    
  • On each of the data node hosts (198.51.100.30 and 198.51.100.40), execute the following command:

    C:\> SC START ndbd
    
  • On the management node host, use the ndb_mgm client to verify that the management node and both data nodes have started successfully (see Section 23.2.2.3, “Initial Startup of NDB Cluster on Windows”).

  • On the SQL node host (198.51.100.20), execute the following command:

    C:\> SC START mysql
    

In a production setting, it is usually not desirable to shut down the cluster completely. In many cases, even when making configuration changes, or performing upgrades to the cluster hardware or software (or both), which require shutting down individual host machines, it is possible to do so without shutting down the cluster as a whole by performing a rolling restart of the cluster. For more information about doing this, see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”.

23.2.7 Upgrading and Downgrading NDB Cluster

This section provides information about NDB Cluster software and table file compatibility between different NDB Cluster 8.0 releases with regard to performing upgrades and downgrades as well as compatibility matrices and notes. You should already be familiar with installing and configuring NDB Cluster prior to attempting an upgrade or downgrade. See Section 23.3, “Configuration of NDB Cluster”.

Schema operations, including SQL DDL statements, cannot be performed while any data nodes are restarting, and thus during an online upgrade or downgrade of the cluster. For other information regarding the rolling restart procedure used to perform an online upgrade, see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”.

Important

Only compatibility between MySQL versions with regard to NDBCLUSTER is taken into account in this section, and there are likely other issues to be considered. As with any other MySQL software upgrade or downgrade, you are strongly encouraged to review the relevant portions of the MySQL Manual for the MySQL versions from which and to which you intend to migrate, before attempting an upgrade or downgrade of the NDB Cluster software. See Section 2.11, “Upgrading MySQL”.

The table shown here provides information on NDB Cluster upgrade and downgrade compatibility among different releases of NDB 8.0. Additional notes about upgrades and downgrades to, from, or within the NDB Cluster 8.0 release series can be found following the table.

Upgrades and Downgrades, NDB Cluster 8.0

Figure 23.5 NDB Cluster Upgrade and Downgrade Compatibility, MySQL NDB Cluster 8.0

Graphical representation of the upgrade/downgrade matrix contained in the file storage/ndb/src/common/util/version.cpp from the MySQL 8.0 source tree.

Version support.  The following versions of NDB Cluster are supported for upgrades to GA releases of NDB Cluster 8.0 (8.0.19 and later):

  • NDB Cluster 7.6: NDB 7.6.4 and later

  • NDB Cluster 7.5: NDB 7.5.4 and later

  • NDB Cluster 7.4: NDB 7.4.6 and later

To upgrade from a release series previous to NDB 7.4, you must upgrade in stages, first to one of the versions just listed, and then from that version to the latest NDB 8.0 release. In such cases, upgrading to the latest NDB 7.6 release is recommended as the first step.

Known Issues.  The following issues are known to occur when upgrading to or between NDB 8.0 releases:

  • Online downgrades from NDB 8.0.14 to previous releases are not supported. Tables created in NDB 8.0.14 are not backwards compatible with previous releases. This is due to a change in usage of the extra metadata property implemented by NDB tables to provide full support for the MySQL data dictionary.

    For more information, see Changes in NDB table extra metadata. See also Chapter 14, MySQL Data Dictionary.

  • Distributed privileges shared between MySQL servers as implemented in prior release series (see Distributed Privileges Using Shared Grant Tables) are not supported in NDB Cluster 8.0. When started, the mysqld supplied with NDB 8.0.16 and later checks for the existence of any grant tables which use the NDB storage engine; if it finds any, it creates local copies (shadow tables) of these using InnoDB. This is true for each MySQL server connected to NDB Cluster. After this has been performed on all MySQL servers acting as NDB Cluster SQL nodes, the NDB grant tables may be safely removed using the ndb_drop_table utility supplied with the NDB Cluster distribution, like this:

    ndb_drop_table -d mysql user db columns_priv tables_priv proxies_priv procs_priv
    

    It is safe to retain the NDB grant tables, but they are not used for access control and are effectively ignored.

    For more information about the MySQL privileges system used in NDB 8.0, see Section 23.5.12, “Distributed MySQL Privileges with NDB_STORED_USER”, as well as Section 6.2.3, “Grant Tables”.

  • In NDB 8.0.18, the binary configuration file format has been enhanced to provide support for greater numbers of nodes than in previous versions. The new format is not accessible to 8.0.17 and older nodes, although newer management servers can detect older nodes and communicate with them using the appropriate format.

    Upgrades to NDB 8.0.18 or later from 8.0.17 and earlier should not be problematic in this regard. In the case of downgrades from NDB 8.0.18 or later to 8.0.17 or earlier, because older management servers cannot read the newer binary configuration file format, some manual intervention is required. When performing such a downgrade, it is necessary to remove any cached binary configuration files prior to starting the management using the older NDB software version, and to have the plaintext configuration file available for the management server to read. Alternatively, you can start the older management server using the --initial option (again, it is necessary to have the config.ini available). If the cluster uses multiple management servers, one of these two things must be done for each management server binary.

    Also in connection with support for increased numbers of nodes, due to incompatible changes implemented in NDB 8.0.18 in the data node LCP Sysfile, it is necessary, when performing an online downgrade from NDB 8.0.18 (or later) to any prior release, to restart all data nodes using the --initial option.

    Restarting the data nodes with --initial is also required when upgrading any release prior to NDB 7.6.4 to any NDB 8.0 release.

  • Direct downgrades of clusters running more than 48 data nodes, or with data nodes using node IDs greater than 48, to NDB versions 8.0.17 and earlier from NDB 8.0.18 or later are not supported. It is necessary in such cases to reduce the number of data nodes, change the configurations for all data nodes such that they use node IDs less than or equal to 48, or both, as required not to exceed the old maximums.

  • If you are downgrading from NDB 8.0 to NDB 7.5 or NDB 7.4, you must set an explicit value for IndexMemory in the cluster configuration file if none is already present. This is because NDB 8.0 does not use this parameter (which was removed in NDB 7.6) and sets it to 0 by default, whereas it is required in NDB 7.5 and NDB 7.4, in both of which the cluster refuses to start with Invalid configuration received from Management Server... if IndexMemory is not set to a nonzero value.

    Setting IndexMemory is not required for downgrades from NDB 8.0 to NDB 7.6.

  • NDB 8.0.22 adds support for IPv6 addressing for management nodes and data nodes in the config.ini file. To begin using IPv6 addresses as part of an upgrade, perform the following steps:

    1. Perform an upgrade of the cluster to version 8.0.22 or a later version of the NDB Cluster software in the usual manner.

    2. Change the addresses used in the config.ini file to IPv6 addresses.

    3. Perform a system restart of the cluster.

23.2.8 The NDB Cluster Auto-Installer (No longer supported)

Note

This feature has been removed from NDB Cluster, and is no longer supported. See Section 23.1.4, “What is New in NDB Cluster”, for more information.

This section describes the web-based graphical configuration installer included as part of the NDB Cluster distribution. Topics discussed include an overview of the installer and its parts, software and other requirements for running the installer, navigating the GUI, and using the installer to set up and start or stop an NDB Cluster on one or more host computers.

The NDB Cluster Auto-Installer is made up of two components. The front end is a GUI client implemented as a Web page that loads and runs in a standard Web browser such as Firefox or Microsoft Internet Explorer. The back end is a server process (ndb_setup.py) that runs on the local machine or on another host to which you have access.

These two components (client and server) communicate with each other using standard HTTP requests and responses. The back end can manage NDB Cluster software programs on any host where the back end user has granted access. If the NDB Cluster software is on a different host, the back end relies on SSH for access.

23.2.8.1 NDB Cluster Auto-Installer Requirements

This section provides information on supported operating platforms and software, required software, and other prerequisites for running the NDB Cluster Auto-Installer.

Supported platforms.  The NDB Cluster Auto-Installer is available with NDB 8.0 distributions for recent versions of Linux, Windows, Solaris, and macOS. For more detailed information about platform support for NDB Cluster and the NDB Cluster Auto-Installer, see https://www.mysql.com/support/supportedplatforms/cluster.html.

Supported web browsers.  The web-based installer is supported with recent versions of Firefox and Microsoft Internet Explorer. It should also work with recent versions of Opera, Safari, and Chrome, although we have not thoroughly tested for compability with these browsers.

Required software—setup host.  The following software must be installed on the host where the Auto-Installer is run:

  • Python 2.6 or higher.  The Auto-Installer requires the Python interpreter and standard libraries. If these are not already installed on the system, you may be able to add them using the system's package manager. Otherwise, you can download them from http://python.org/download/.

  • Paramiko 2 or higher.  You can download this from http://www.lag.net/paramiko/ if it is not available from your system's package manager.

  • Pycrypto version 1.9 or higher.  This cryptography module is required by Paramiko, and can be iunstalled using pip install cryptography. If pip is not installed, and the module is not available using your system's package manage, you can download it from https://www.dlitz.net/software/pycrypto/.

All of the software in the preceding list is included in the Windows version of the configuration tool, and does not need to be installed separately.

Required software—remote hosts.  The only software required for remote hosts where you wish to deploy NDB Cluster nodes is the SSH server, which is usually installed by default on Linux and Solaris systems. Several alternatives are available for Windows; for an overview of these, see http://en.wikipedia.org/wiki/Comparison_of_SSH_servers.

An additional requirement when using multiple hosts is that it is possible to authenticate to any of the remote hosts using SSH and the proper keys or user credentials, as discussed in the next few paragraphs:

Authentication and security.  Three basic security or authentication mechanisms for remote access are available to the Auto-Installer, which we list and describe here:

  • SSH.  A secure shell connection is used to enable the back end to perform actions on remote hosts. For this reason, an SSH server must be running on the remote host. In addition, the operating system user running the installer must have access to the remote server, either with a user name and password, or by using public and private keys.

    Important

    You should never use the system root account for remote access, as this is extremely insecure. In addition, mysqld cannot normally be started by system root. For these and other reasons, you should provide SSH credentials for a regular user account on the target system, and not for system root. For more information about this issue, see Section 6.1.5, “How to Run MySQL as a Normal User”.

  • HTTPS.  Remote communication between the Web browser front end and the back end is not encrypted by default, which means that information such as the user's SSH password is transmitted as cleartext that is readable to anyone. For communication from a remote client to be encrypted, the back end must have a certificate, and the front end must communicate with the back end using HTTPS rather than HTTP. Enabling HTTPS is accomplished most easily through issuing a self-signed certificate. Once the certificate is issued, you must make sure that it is used. You can do this by starting ndb_setup.py from the command line with the --use-https (-S) and --cert-file (-c) options.

    A sample certificate file cfg.pem is included and is used by default. This file is located in the mcc directory under the installation share directory; on Linux, the full path to the file is normally /usr/share/mysql/mcc/cfg.pem. On Windows systems, this is usually C:\Program Files\MySQL\MySQL Server 8.0\share\mcc\cfg.pem. Letting the default be used means that, for testing purposes, you can simply start the installer with the -S option to use an HTTPS connection between the browser and the back end.

    The Auto-Installer saves the configuration file for a given cluster mycluster01 as mycluster01.mcc in the home directory of the user invoking the ndb_setup.py executable. This file is encrypted with a passphrase supplied by the user (using Fernet); because HTTP transmits the passphrase in the clear, it is strongly recommended that you always use an HTTPS connection to access the Auto-Installer on a remote host.

  • Certificate-based authentication.  The back end ndb_setup.py process can execute commands on the local host as well as remote hosts. This means that anyone connecting to the back end can take charge of how commands are executed. To reject unwanted connections to the back end, a certificate may be required for authentication of the client. In this case, a certificate must be issued by the user, installed in the browser, and made available to the back end for authentication purposes. You can enact this requirement (together with or in place of password or key authentication) by starting ndb_setup.py with the --ca-certs-file (-a) option.

There is no need or requirement for secure authentication when the client browser is running on the same host as the Auto-Installer back end.

See also Section 23.5.17, “NDB Cluster Security Issues”, which discusses security considerations to take into account when deploying NDB Cluster, as well as Chapter 6, Security, for more general MySQL security information.

23.2.8.2 Using the NDB Cluster Auto-Installer

The NDB Cluster Auto-Installer interface is made up of several pages, each corresponding to a step in the process used to configure and deploy an NDB Cluster. These pages are listed here, in order:

  • Welcome: Begin using the Auto-Installer by choosing either to configure a new NDB Cluster, or to continue configuring an existing one.

  • Define Cluster: Set basic information about the cluster as a whole, such as name, hosts, and load type. Here you can also set the SSH authentication type for accessing remote hosts, if needed.

  • Define Hosts: Identify the hosts where you intend to run NDB Cluster processes.

  • Define Processes: Assign one or more processes of a given type or types to each cluster host.

  • Define Parameters: Set configuration attributes for processes or types of processes.

  • Deploy Configuration: Deploy the cluster with the configuration set previously; start and stop the deployed cluster.

NDB Cluster Installer Settings and Help Menus

These menus are shown on all screens except for the Welcome screen. They provide access to installer settings and information. The Settings menu is shown here in more detail:

Figure 23.6 NDB Cluster Auto-Installer Settings menu

Content is described in the surrounding text.

The Settings menu has the following entries:

  • Automatically save configuration as cookies: Save your configuration information—such as host names, process data, and parameter values—as a cookie in the browser. When this option is chosen, all information except any SSH password is saved. This means that you can quit and restart the browser, and continue working on the same configuration from where you left off at the end of the previous session. This option is enabled by default.

    The SSH password is never saved; if you use one, you must supply it at the beginning of each new session.

  • Show advanced configuration options: Shows by default advanced configuration parameters where available.

    Once set, the advanced parameters continue to be used in the configuration file until they are explicitly changed or reset. This is regardless of whether the advanced parameters are currently visible in the installer; in other words, disabling the menu item does not reset the values of any of these parameters.

    You can also toggle the display of advanced parameters for individual processes on the Define Parameters screen.

    This option is disabled by default.

  • Automatically get resource information for new hosts: Query new hosts automatically for hardware resource information to pre-populate a number of configuration options and values. In this case, the suggested values are not mandatory, but they are used unless explicitly changed using the appropriate editing options in the installer.

    This option is enabled by default.

The installer Help menu is shown here:

Figure 23.7 NDB Cluster Auto-Installer Help menu

Content is described in the surrounding text.

The Help menu provides several options, described in the following list:

  • Contents: Show the built-in user guide. This is opened in a separate browser window, so that it can be used simultaneously with the installer without interrupting workflow.

  • Current page: Open the built-in user guide to the section describing the page currently displayed in the installer.

  • About: open a dialog displaying the installer name and the version number of the NDB Cluster distribution with which it was supplied.

The Auto-Installer also provides context-sensitive help in the form of tooltips for most input widgets.

In addition, the names of most NDB configuration parameters are linked to their descriptions in the online documentation. The documentation is displayed in a separate browser window.

The next section discusses starting the Auto-Installer. The sections immediately following it describe in greater detail the purpose and function of each of these pages in the order listed previously.

Starting the NDB Cluster Auto-Installer

The Auto-Installer is provided together with the NDB Cluster software. Separate RPM and .deb packages containing only the Auto-Installer are also available for many Linux distributions. (See Section 23.2, “NDB Cluster Installation”.)

The present section explains how to start the installer. You can do by invoking the ndb_setup.py executable.

User and privileges

You should run the ndb_setup.py as a normal user; no special privileges are needed to do so. You should not run this program as the mysql user, or using the system root or Administrator account; doing so may cause the installation to fail.

ndb_setup.py is found in the bin within the NDB Cluster installation directory; a typical location might be /usr/local/mysql/bin on a Linux system or C:\Program Files\MySQL\MySQL Server 8.0\bin on a Windows system. This can vary according to where the NDB Cluster software is installed on your system, and the installation method.

On Windows, you can also start the installer by running setup.bat in the NDB Cluster installation directory. When invoked from the command line, this batch file accepts the same options as ndb_setup.py.

ndb_setup.py can be started with any of several options that affect its operation, but it is usually sufficient to allow the default settings be used, in which case you can start ndb_setup.py by either of the following two methods:

  1. Navigate to the NDB Cluster bin directory in a terminal and invoke it from the command line, without any additional arguments or options, like this:

    shell> ndb_setup.py
    Running out of install dir: /usr/local/mysql/bin
    Starting web server on port 8081
    URL is https://localhost:8081/welcome.html
    deathkey=627876
    Press CTRL+C to stop web server.
    The application should now be running in your browser.
    (Alternatively you can navigate to https://localhost:8081/welcome.html to start it)
    

    This works regardless of operating platform.

  2. Navigate to the NDB Cluster bin directory in a file browser (such as Windows Explorer on Windows, or Konqueror, Dolphin, or Nautilus on Linux) and activate (usually by double-clicking) the ndb_setup.py file icon. This works on Windows, and should work with most common Linux desktops as well.

    On Windows, you can also navigate to the NDB Cluster installation directory and activate the setup.bat file icon.

In either case, once ndb_setup.py is invoked, the Auto-Installer's Welcome screen should open in the system's default web browser. If not, you should be able to open the page http://localhost:8081/welcome.html or https://localhost:8081/welcome.html manually in the browser.

In some cases, you may wish to use non-default settings for the installer, such as specifying HTTPS for connections, or a different port for the Auto-Installer's included web server to run on, in which case you must invoke ndb_setup.py with one or more startup options with values overriding the necessary defaults. The same startup options can be used on Windows systems with the setup.bat file supplied for such platforms in the NDB Cluster software distribution. This can be done using the command line, but if you want or need to start the installer from a desktop or file browser while employing one or more of these options, it is also possible to create a script or batch file containing the proper invocation, then to double-click its file icon in the file browser to start the installer. (On Linux systems, you might also need to make the script file executable first.) If you plan to use the Auto-Installer from a remote host, you should start using the -S option. For information about this and other advanced startup options for the NDB Cluster Auto-Installer, see Section 23.4.26, “ndb_setup.py — Start browser-based Auto-Installer for NDB Cluster (DEPRECATED)”.

NDB Cluster Auto-Installer Welcome Screen

The Welcome screen is loaded in the default browser when ndb_setup.py is invoked. The first time the Auto-Installer is run (or if for some other reason there are no existing configurations), this screen appears as shown here:

Figure 23.8 The NDB Cluster Auto-Installer Welcome screen, first run

Content is described in the surrounding text.

In this case, the only choice of cluster listed is for configuration of a new cluster, and both the View Cfg and Continue buttons are inactive.

To create a new configuration, enter and confirm a passphrase in the text boxes provided. When this has been done, you can click Continue to proceed to the Define Cluster screen where you can assign a name to the new cluster.

If you have previously created one or more clusters with the Auto-Installer, they are listed by name. This example shows an existing cluster named mycluster-1:

Figure 23.9 The NDB Cluster Auto-Installer Welcome screen, with previously created cluster mycluster-1

Content is described in the surrounding text.

To view the configuration for and work with a given cluster, select the radiobutton next to its name in the list, then enter and confirm the passphrase that was used to create it. When you have done this correctly, you can click View Cfg to view and edit this cluster's configuration.

NDB Cluster Auto-Installer Define Cluster Screen

The Define Cluster screen is appears following the Welcome screen, and is used for setting general properties of the cluster. The layout of the Define Cluster screen is shown here:

Figure 23.10 The NDB Cluster Auto-Installer Define Cluster screen

Content is described in the surrounding text.

This screen and subsequent screens also include Settings and Help menus which are described later in this section; see NDB Cluster Installer Settings and Help Menus.

The Define Cluster screen allows you to set three sorts of properties for the cluster: cluster properties, SSH properties, and installation properties.

Cluster properties that can be set on this screen are listed here:

  • Cluster name: A name that identifies the cluster; in this example, this is mycluster-1. The name is set on the previous screen and cannot be changed here.

  • Host list: A comma-delimited list of one or more hosts where cluster processes should run. By default, this is 127.0.0.1. If you add remote hosts to the list, you must be able to connect to them using the credentials supplied as SSH properties.

  • Application type: Choose one of the following:

    1. Simple testing: Minimal resource usage for small-scale testing. This the default. Not intended for production environments.

    2. Web: Maximize performance for the given hardware.

    3. Real-time: Maximize performance while maximizing sensitivity to timeouts in order to minimize the time needed to detect failed cluster processes.

  • Write load: Choose a level for the anticipated number of writes for the cluster as a whole. You can choose any one of the following levels:

    1. Low: The expected load includes fewer than 100 write transactions for second.

    2. Medium: The expected load includes 100 to 1000 write transactions per second; this is the default.

    3. High: The expected load includes more than 1000 write transactions per second.

SSH properties are described in the following list:

  • Key-Based SSH: Check this box to use key-enabled login to the remote host. If checked, the key user and passphrase must also be supplied; otherwise, a user and password for a remote login account are needed.

  • User: Name of user with remote login access.

  • Password: Password for remote user.

  • Key user: Name of the user for whom the key is valid, if not the same as the operating system user.

  • Key passphrase: Passphrase for the key, if required.

  • Key file: Path to the key file. The default is ~/.ssh/id_rsa.

The SSH properties set on this page apply to all hosts in the cluster. They can be overridden for a given host by editing that hosts's properties on the Define Hosts screen.

Two installation properties can also be set on this screen:

  • Install MySQL Cluster: This setting determines the source from which the Auto-Installer installs NDB Cluster software, if any, on the cluster hosts. Possible values and their effects are listed here:

    1. DOCKER: Try to install the MySQL Cluster Docker image from https://hub.docker.com/r/mysql/mysql-cluster/ on each host

    2. REPO: Try to install the NDB Cluster software from the MySQL Repositories on each host

    3. BOTH: Try to install either the Docker image or the software from the repository on each host, giving preference to the repository

    4. NONE: Do not install the NDB Cluster software on the hosts; this is the default

  • Open FW Ports: Check this check box to have the installer attempt to open ports required by NDB CLuster processes on all hosts.

The next figure shows the Define Cluster page with settings for a small test cluster with all nodes running on localhost:

Figure 23.11 The NDB Cluster Auto-Installer Define Cluster screen, with settings for a test cluster

Content is described in the surrounding text.

After making the desired settings, you can save them to the configuration file and proceed to the Define Hosts screen by clicking the Save & Next button.

If you exit the installer without saving, no changes are made to the configuration file.

NDB Cluster Auto-Installer Define Hosts Screen

The Define Hosts screen, shown here, provides a means of viewing and specifying several key properties of each cluster host:

Figure 23.12 NDB Cluster Define Hosts screen, start

Content is described in the surrounding text.

Properties shown include the following:

  • Host: Name or IP address of this host

  • Res.info: Shows OK if the installer was able to retrieve requested resource information from this host

  • Platform: Operating system or platform

  • Memory (MB): Amount of RAM on this host

  • Cores: Number of CPU cores available on this host

  • MySQL Cluster install directory: Path to directory where the NDB Cluster software is installed on this host; defaults to /usr/local/bin

  • MySQL Cluster data directory: Path to directory used for data by NDB Cluster processes on this host; defaults to /var/lib/mysql-cluster.

  • DiskFree: Free disk space in bytes

    For hosts with multiple disks, only the space available on the disk used for the data directory is shown.

This screen also provides an extended view for each host that includes the following properties:

  • FDQN: This host's fully qualified domain name, used by the installer to connect with it, distribute configuration information to it, and start and stop cluster processes on it.

  • Internal IP: The IP address used for communication with cluster processes running on this host by processes running elsewhere.

  • OS Details: Detailed operating system name and version information.

  • Open FW: If this check box is enabled, the installer attempts to open ports in the host's firewall needed by cluster processes.

  • REPO URL: URL for MySQL NDB Cluster repository

  • DOCKER URL: URL for MySQL NDB CLuster Docker images; for NDB 8.0, this is mysql/mysql-cluster:8.0.

  • Install: If this check box is enabled, the Auto-Installer attempts to install the NDB Cluster software on this host

The extended view is shown here:

Figure 23.13 NDB Cluster Define Hosts screen, extended host info view

Content is described in the surrounding text.

All cells in the display are editable, with the exceptions of those in the Host, Res.info, and FQDN columns.

Be aware that it may take some time for information to be retrieved from remote hosts. Fields for which no value could be retrieved are indicated with an ellipsis (). You can retry the fetching of resource information from one or more hosts by selecting the hosts in the list and then clicking the Refresh selected host(s) button.

Adding and Removing Hosts

You can add one or more hosts by clicking the Add Host button and entering the required properties where indicated in the Add new host dialog, shown here:

Figure 23.14 NDB Cluster Add Host dialog

Content is described in the surrounding text.

This dialog includes the following fields:

  • Host name: A comma-separated list of one or more host names, IP addresses, or both. These must be accessible from the host where the Auto-Installer is running.

  • Host internal IP (VPN): If you are setting up the cluster to run on a VPN or other internal network, enter the IP address or addresses used for contact by cluster nodes on other hosts.

  • Key-based auth: If checked, enables key-based authentication. You can enter any additional needed information in the User, Passphrase, and Key file fields.

  • Ordinary login: If accessing this host using a password-based login, enter the appropriate information in the User and Password fields.

  • Open FW ports: Selecting this check box allows the installer try opening any ports needed by cluster processes in this host's firewall.

  • Configure installation: Checking this allows the Auto-Install to attempt to set up the NDB Cluster software on this host.

To save the new host and its properties, click Add. If you wish to cancel without saving any changes, click Cancel instead.

Similarly, you can remove one or more hosts using the button labelled Remove selected host(s). When you remove a host, any process which was configured for that host is also removed.

Warning

Remove selected host(s) acts immediately. There is no confirmation dialog. If you remove a host in error, you must re-enter its name and properties manually using Add host.

If the SSH user credentials on the Define Cluster screen are changed, the Auto-Installer attempts to refresh the resource information from any hosts for which information is missing.

You can edit the host's platform name, hardware resource information, installation directory, and data directory by clicking the corresponding cell in the grid, by selecting one or more hosts and clicking the button labelled Edit selected host(s). This causes a dialog box to appear, in which these fields can be edited, as shown here:

Figure 23.15 NDB Cluster Auto-Installer Edit Hosts dialog

Content is described in the surrounding text.

When more than one host is selected, any edited values are applied to all selected hosts.

Once you have entered all desired host information, you can use the Save & Next button to save the information to the cluster's configuration file and proceed to the Define Processes screen, where you can set up NDB Cluster processes on one or more hosts.

NDB Cluster Auto-Installer Define Processes Screen

The Define Processes screen, shown here, provides a way to assign NDB Cluster processes (nodes) to cluster hosts:

Figure 23.16 NDB Cluster Auto-Installer Define Processes dialog

Content is described in the surrounding text. The example process tree topology includes "Any host" and "localhost", as defined earlier. The localhost tree includes the following processes: Management mode 1, API node 1, API node 2, API node 3, SQL node 1, SQL node 2, Multi threaded data node 1, and Multi threaded data node 2. This panel also includes "Add process" and "Del[ete] process" buttons.

This screen contains a process tree showing cluster hosts and processes set up to run on each one, as well as a panel which displays information about the item currently selected in the tree.

When this screen is accessed for the first time for a given cluster, a default set of processes is defined for you, based on the number of hosts. If you later return to the Define Hosts screen, remove all hosts, and add new hosts, this also causes a new default set of processes to be defined.

NDB Cluster processes are of the types described in this list:

  • Management node.  Performs administrative tasks such as stopping individual data nodes, querying node and cluster status, and making backups. Executable: ndb_mgmd.

  • Single-threaded data node.  Stores data and executes queries. Executable: ndbd.

  • Multi threaded data node.  Stores data and executes queries with multiple worker threads executing in parallel. Executable: ndbmtd.

  • SQL node.  MySQL server for executing SQL queries against NDB. Executable: mysqld.

  • API node.  A client accessing data in NDB by means of the NDB API or other low-level client API, rather than by using SQL. See MySQL NDB Cluster API Developer Guide, for more information.

For more information about process (node) types, see Section 23.1.1, “NDB Cluster Core Concepts”.

Processes shown in the tree are numbered sequentially by type, for each host—for example, SQL node 1, SQL node 2, and so on—to simplify identification.

Each management node, data node, or SQL process must be assigned to a specific host, and is not allowed to run on any other host. An API node may be assigned to a single host, but this is not required. Instead, you can assign it to the special Any host entry which the tree also contains in addition to any other hosts, and which acts as a placeholder for processes that are allowed to run on any host. Only API processes may use this Any host entry.

Adding processes.  To add a new process to a given host, either right-click that host's entry in the tree, then select the Add process popup when it appears, or select a host in the process tree, and press the Add process button below the process tree. Performing either of these actions opens the add process dialog, as shown here:

Figure 23.17 NDB Cluster Auto-Installer Add Process Dialog

Most content is described in the surrounding text. Shows a window titled "Add new process" with two options: "Select process type:" that shows a select box with "API node" selected, and "Enter process name:" with "API node 4" entered as plain text. Action buttons include "Cancel" and "Add".

Here you can select from among the available process types described earlier this section; you can also enter an arbitrary process name to take the place of the suggested value, if desired.

Removing processes.  To delete a process, select that process in the tree and use the Del process button.

When you select a process in the process tree, information about that process is displayed in the information panel, where you can change the process name and possibly its type. You can change a multi-threaded data node (ndbmtd) to a single-threaded data node (ndbd), or the reverse, only; no other process type changes are allowed. If you want to make a change between any other process types, you must delete the original process first, then add a new process of the desired type.

NDB Cluster Auto-Installer Define Parameters Screen

Like the Define Processes screen, this screen includes a process tree; the Define Parameters process tree is organized by process or node type, in groups labelled Management Layer, Data Layer, SQL Layer, and API Layer. An information panel displays information regarding the item currently selected. The Define Attributes screen is shown here:

Figure 23.18 NDB Cluster Auto-Installer Define Parameters screen

Content is described in the surrounding text.

The check box labelled Show advanced configuration, when checked, makes advanced options for data node and SQL node processes visible in the information pane. These options are set and used whether or not they are visible. You can also enable this behavior globally by checking Show advanced configuration options under Settings (see NDB Cluster Installer Settings and Help Menus).

You can edit attributes for a single process by selecting that process from the tree, or for all processes of the same type in the cluster by selecting one of the Layer folders. A per-process value set for a given attribute overrides any per-group setting for that attribute that would otherwise apply to the process in question. An example of such an information panel (for an SQL process) is shown here:

Figure 23.19 Define Parameters—Process Attributes

Content is described in the surrounding text.

Attributes whose values can be overridden are shown in the information panel with a button bearing a plus sign. This + button activates an input widget for the attribute, enabling you to change its value. When the value has been overridden, this button changes into a button showing an X. The X button undoes any changes made to a given attribute, which immediately reverts to the predefined value.

All configuration attributes have predefined values calculated by the installer, based such factors as host name, node ID, node type, and so on. In most cases, these values may be left as they are. If you are not familiar with it already, it is highly recommended that you read the applicable documentation before making changes to any of the attribute values. To make finding this information easier, each attribute name shown in the information panel is linked to its description in the online NDB Cluster documentation.

NDB Cluster Auto-Installer Deploy Configuration Screen

This screen allows you to perform the following tasks:

  • Review process startup commands and configuration files to be applied

  • Distribute configuration files by creating any necessary files and directories on all cluster hosts—that is, deploy the cluster as presently configured

  • Start and stop the cluster

The Deploy Configuration screen is shown here:

Figure 23.20 NDB Cluster Auto-Installer Deploy Configuration screen

Content is described in the surrounding text.

Like the Define Parameters screen, this screen features a process tree which is organized by process type. Next to each process in the tree is a status icon indicating the current status of the process: connected (CONNECTED), starting (STARTING), running (STARTED), stopping (STOPPING), or disconnected (NO_CONTACT). The icon shows green if the process is connected or running; yellow if it is starting or stopping; red if the process is stopped or cannot be contacted by the management server.

This screen also contains two information panels, one showing the startup command or commands needed to start the selected process. (For some processes, more than one command may be required—for example, if initialization is necessary.) The other panel shows the contents of the configuration file, if any, for the given process.

This screen also contains four buttons, labelled as and performing the functions described in the following list:

  • Install cluster: Nonfunctional in this release; implementation intended for a future release.

  • Deploy cluster: Verify that the configuration is valid. Create any directories required on the cluster hosts, and distribute the configuration files onto the hosts. A progress bar shows how far the deployment has proceeded, as shown here, and a dialog is pisplayed when the deployment has completed, as shown here:

    Figure 23.21 Cluster Deployment Process

    Content is described in the surrounding text.

  • Start cluster: The cluster is deployed as with Deploy cluster, after which all cluster processes are started in the correct order.

    Starting these processes may take some time. If the estimated time to completion is too large, the installer provides an opportunity to cancel or to continue of the startup procedure. A progress bar indicates the current status of the startup procedure, as shown here:

    Figure 23.22 Cluster Startup Process with Progress Bar

    Content is described in the surrounding text.

    The process status icons next to the items shown in the process tree also update with the status of each process.

    A confirmation dialog is shown when the startup process has completed, as shown here:

    Figure 23.23 Cluster Startup, Process Completed Dialog

    Content is described in the surrounding text.

  • Stop cluster: After the cluster has been started, you can stop it using this. As with starting the cluster, cluster shutdown is not instantaneous, and may require some time complete. A progress bar, similar to that displayed during cluster startup, shows the approximate current status of the cluster shutdown procedure, as do the process status icons adjoining the process tree. The progress bar is shown here:

    Figure 23.24 Cluster Shutdown Process, with Progress Bar

    Content is described in the surrounding text.

    A confirmation dialog indicates when the shutdown process is complete:

    Figure 23.25 Cluster Shutdown, Process Completed Dialog

    Content is described in the surrounding text.

The Auto-Installer generates a config.ini file containing NDB node parameters for each management node, as well as a my.cnf file containing the appropriate options for each mysqld process in the cluster. No configuration files are created for data nodes or API nodes.

23.3 Configuration of NDB Cluster

A MySQL server that is part of an NDB Cluster differs in one chief respect from a normal (nonclustered) MySQL server, in that it employs the NDB storage engine. This engine is also referred to sometimes as NDBCLUSTER, although NDB is preferred.

To avoid unnecessary allocation of resources, the server is configured by default with the NDB storage engine disabled. To enable NDB, you must modify the server's my.cnf configuration file, or start the server with the --ndbcluster option.

This MySQL server is a part of the cluster, so it also must know how to access a management node to obtain the cluster configuration data. The default behavior is to look for the management node on localhost. However, should you need to specify that its location is elsewhere, this can be done in my.cnf, or with the mysql client. Before the NDB storage engine can be used, at least one management node must be operational, as well as any desired data nodes.

For more information about --ndbcluster and other mysqld options specific to NDB Cluster, see Section 23.3.3.9.1, “MySQL Server Options for NDB Cluster”.

For general information about installing NDB Cluster, see Section 23.2, “NDB Cluster Installation”.

23.3.1 Quick Test Setup of NDB Cluster

To familiarize you with the basics, we describe the simplest possible configuration for a functional NDB Cluster. After this, you should be able to design your desired setup from the information provided in the other relevant sections of this chapter.

First, you need to create a configuration directory such as /var/lib/mysql-cluster, by executing the following command as the system root user:

shell> mkdir /var/lib/mysql-cluster

In this directory, create a file named config.ini that contains the following information. Substitute appropriate values for HostName and DataDir as necessary for your system.

# file "config.ini" - showing minimal setup consisting of 1 data node,
# 1 management server, and 3 MySQL servers.
# The empty default sections are not required, and are shown only for
# the sake of completeness.
# Data nodes must provide a hostname but MySQL Servers are not required
# to do so.
# If you don't know the hostname for your machine, use localhost.
# The DataDir parameter also has a default value, but it is recommended to
# set it explicitly.
# Note: [db], [api], and [mgm] are aliases for [ndbd], [mysqld], and [ndb_mgmd],
# respectively. [db] is deprecated and should not be used in new installations.

[ndbd default]
NoOfReplicas= 1

[mysqld  default]
[ndb_mgmd default]
[tcp default]

[ndb_mgmd]
HostName= myhost.example.com

[ndbd]
HostName= myhost.example.com
DataDir= /var/lib/mysql-cluster

[mysqld]
[mysqld]
[mysqld]

You can now start the ndb_mgmd management server. By default, it attempts to read the config.ini file in its current working directory, so change location into the directory where the file is located and then invoke ndb_mgmd:

shell> cd /var/lib/mysql-cluster
shell> ndb_mgmd

Then start a single data node by running ndbd:

shell> ndbd

For command-line options which can be used when starting ndbd, see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

By default, ndbd looks for the management server at localhost on port 1186.

Note

If you have installed MySQL from a binary tarball, you must to specify the path of the ndb_mgmd and ndbd servers explicitly. (Normally, these can be found in /usr/local/mysql/bin.)

Finally, change location to the MySQL data directory (usually /var/lib/mysql or /usr/local/mysql/data), and make sure that the my.cnf file contains the option necessary to enable the NDB storage engine:

[mysqld]
ndbcluster

You can now start the MySQL server as usual:

shell> mysqld_safe --user=mysql &

Wait a moment to make sure the MySQL server is running properly. If you see the notice mysql ended, check the server's .err file to find out what went wrong.

If all has gone well so far, you now can start using the cluster. Connect to the server and verify that the NDBCLUSTER storage engine is enabled:

shell> mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1 to server version: 8.0.24

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> SHOW ENGINES\G
...
*************************** 12. row ***************************
Engine: NDBCLUSTER
Support: YES
Comment: Clustered, fault-tolerant, memory-based tables
*************************** 13. row ***************************
Engine: NDB
Support: YES
Comment: Alias for NDBCLUSTER
...

The row numbers shown in the preceding example output may be different from those shown on your system, depending upon how your server is configured.

Try to create an NDBCLUSTER table:

shell> mysql
mysql> USE test;
Database changed

mysql> CREATE TABLE ctest (i INT) ENGINE=NDBCLUSTER;
Query OK, 0 rows affected (0.09 sec)

mysql> SHOW CREATE TABLE ctest \G
*************************** 1. row ***************************
       Table: ctest
Create Table: CREATE TABLE `ctest` (
  `i` int(11) default NULL
) ENGINE=ndbcluster DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

To check that your nodes were set up properly, start the management client:

shell> ndb_mgm

Use the SHOW command from within the management client to obtain a report on the cluster's status:

ndb_mgm> SHOW
Cluster Configuration
---------------------
[ndbd(NDB)]     1 node(s)
id=2    @127.0.0.1  (Version: 8.0.23-ndb-8.0.23, Nodegroup: 0, *)

[ndb_mgmd(MGM)] 1 node(s)
id=1    @127.0.0.1  (Version: 8.0.23-ndb-8.0.23)

[mysqld(API)]   3 node(s)
id=3    @127.0.0.1  (Version: 8.0.23-ndb-8.0.23)
id=4 (not connected, accepting connect from any host)
id=5 (not connected, accepting connect from any host)

At this point, you have successfully set up a working NDB Cluster . You can now store data in the cluster by using any table created with ENGINE=NDBCLUSTER or its alias ENGINE=NDB.

23.3.2 Overview of NDB Cluster Configuration Parameters, Options, and Variables

The next several sections provide summary tables of NDB Cluster node configuration parameters used in the config.ini file to govern various aspects of node behavior, as well as of options and variables read by mysqld from a my.cnf file or from the command line when run as an NDB Cluster process. Each of the node parameter tables lists the parameters for a given type (ndbd, ndb_mgmd, mysqld, computer, tcp, or shm). All tables include the data type for the parameter, option, or variable, as well as its default, mimimum, and maximum values as applicable.

Considerations when restarting nodes.  For node parameters, these tables also indicate what type of restart is required (node restart or system restart)—and whether the restart must be done with --initial—to change the value of a given configuration parameter. When performing a node restart or an initial node restart, all of the cluster's data nodes must be restarted in turn (also referred to as a rolling restart). It is possible to update cluster configuration parameters marked as node online—that is, without shutting down the cluster—in this fashion. An initial node restart requires restarting each ndbd process with the --initial option.

A system restart requires a complete shutdown and restart of the entire cluster. An initial system restart requires taking a backup of the cluster, wiping the cluster file system after shutdown, and then restoring from the backup following the restart.

In any cluster restart, all of the cluster's management servers must be restarted for them to read the updated configuration parameter values.

Important

Values for numeric cluster parameters can generally be increased without any problems, although it is advisable to do so progressively, making such adjustments in relatively small increments. Many of these can be increased online, using a rolling restart.

However, decreasing the values of such parameters—whether this is done using a node restart, node initial restart, or even a complete system restart of the cluster—is not to be undertaken lightly; it is recommended that you do so only after careful planning and testing. This is especially true with regard to those parameters that relate to memory usage and disk space, such as MaxNoOfTables, MaxNoOfOrderedIndexes, and MaxNoOfUniqueHashIndexes. In addition, it is the generally the case that configuration parameters relating to memory and disk usage can be raised using a simple node restart, but they require an initial node restart to be lowered.

Because some of these parameters can be used for configuring more than one type of cluster node, they may appear in more than one of the tables.

Note

4294967039 often appears as a maximum value in these tables. This value is defined in the NDBCLUSTER sources as MAX_INT_RNIL and is equal to 0xFFFFFEFF, or 232 − 28 − 1.

23.3.2.1 NDB Cluster Data Node Configuration Parameters

The listings in this section provide information about parameters used in the [ndbd] or [ndbd default] sections of a config.ini file for configuring NDB Cluster data nodes. For detailed descriptions and other additional information about each of these parameters, see Section 23.3.3.6, “Defining NDB Cluster Data Nodes”.

These parameters also apply to ndbmtd, the multithreaded version of ndbd. For more information, see Section 23.4.3, “ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)”.

  • Arbitration: How arbitration should be performed to avoid split-brain issues in event of node failure.

  • ArbitrationTimeout: Maximum time (milliseconds) database partition waits for arbitration signal.

  • BackupDataBufferSize: Default size of databuffer for backup (in bytes).

  • BackupDataDir: Path to where to store backups. Note that string '/BACKUP' is always appended to this setting, so that *effective* default is FileSystemPath/BACKUP.

  • BackupDiskWriteSpeedPct: Sets percentage of data node's allocated maximum write speed (MaxDiskWriteSpeed) to reserve for LCPs when starting backup.

  • BackupLogBufferSize: Default size of log buffer for backup (in bytes).

  • BackupMaxWriteSize: Maximum size of file system writes made by backup (in bytes).

  • BackupMemory: Total memory allocated for backups per node (in bytes).

  • BackupReportFrequency: Frequency of backup status reports during backup in seconds.

  • BackupWriteSize: Default size of file system writes made by backup (in bytes).

  • BatchSizePerLocalScan: Used to calculate number of lock records for scan with hold lock.

  • BuildIndexThreads: Number of threads to use for building ordered indexes during system or node restart. Also applies when running ndb_restore --rebuild-indexes. Setting this parameter to 0 disables multithreaded building of ordered indexes.

  • CompressedBackup: Use zlib to compress backups as they are written.

  • CompressedLCP: Write compressed LCPs using zlib.

  • ConnectCheckIntervalDelay: Time between data node connectivity check stages. Data node is considered suspect after 1 interval and dead after 2 intervals with no response.

  • CrashOnCorruptedTuple: When enabled, forces node to shut down whenever it detects corrupted tuple.

  • DataDir: Data directory for this node.

  • DataMemory: Number of bytes on each data node allocated for storing data; subject to available system RAM and size of IndexMemory.

  • DefaultHashMapSize: Set size (in buckets) to use for table hash maps. Three values are supported: 0, 240, and 3840..

  • DictTrace: Enable DBDICT debugging; for NDB development.

  • DiskDataUsingSameDisk: Set to false if Disk Data tablespaces are located on separate physical disks.

  • DiskIOThreadPool: Number of unbound threads for file access, applies to disk data only.

  • Diskless: Run without using disk.

  • DiskPageBufferEntries: Memory to allocate in DiskPageBufferMemory; very large disk transactions may require increasing this value.

  • DiskPageBufferMemory: Number of bytes on each data node allocated for disk page buffer cache.

  • DiskSyncSize: Amount of data written to file before synch is forced.

  • EnablePartialLcp: Enable partial LCP (true); if this is disabled (false), all LCPs write full checkpoints.

  • EnableRedoControl: Enable adaptive checkpointing speed for controlling redo log usage.

  • EventLogBufferSize: Size of circular buffer for NDB log events within data nodes.

  • ExecuteOnComputer: String referencing earlier defined COMPUTER.

  • ExtraSendBufferMemory: Memory to use for send buffers in addition to any allocated by TotalSendBufferMemory or SendBufferMemory. Default (0) allows up to 16MB.

  • FileSystemPath: Path to directory where data node stores its data (directory must exist).

  • FileSystemPathDataFiles: Path to directory where data node stores its Disk Data files. Default value is FilesystemPathDD, if set; otherwise, FilesystemPath is used if it is set; otherwise, value of DataDir is used.

  • FileSystemPathDD: Path to directory where data node stores its Disk Data and undo files. Default value is FileSystemPath, if set; otherwise, value of DataDir is used.

  • FileSystemPathUndoFiles: Path to directory where data node stores its undo files for Disk Data. Default value is FilesystemPathDD, if set; otherwise, FilesystemPath is used if it is set; otherwise, value of DataDir is used.

  • FragmentLogFileSize: Size of each redo log file.

  • HeartbeatIntervalDbApi: Time between API node-data node heartbeats. (API connection closed after 3 missed heartbeats).

  • HeartbeatIntervalDbDb: Time between data node-to-data node heartbeats; data node considered dead after 3 missed heartbeats.

  • HeartbeatOrder: Sets order in which data nodes check each others' heartbeats for determining whether given node is still active and connected to cluster. Must be zero for all data nodes or distinct nonzero values for all data nodes; see documentation for further guidance.

  • HostName: Host name or IP address for this data node.

  • IndexMemory: Number of bytes on each data node allocated for storing indexes; subject to available system RAM and size of DataMemory.

  • IndexStatAutoCreate: Enable/disable automatic statistics collection when indexes are created.

  • IndexStatAutoUpdate: Monitor indexes for changes and trigger automatic statistics updates.

  • IndexStatSaveScale: Scaling factor used in determining size of stored index statistics.

  • IndexStatSaveSize: Maximum size in bytes for saved statistics per index.

  • IndexStatTriggerPct: Threshold percent change in DML operations for index statistics updates. Value is scaled down by IndexStatTriggerScale.

  • IndexStatTriggerScale: Scale down IndexStatTriggerPct by this amount, multiplied by base 2 logarithm of index size, for large index. Set to 0 to disable scaling.

  • IndexStatUpdateDelay: Minimum delay between automatic index statistics updates for given index. 0 means no delay.

  • InitFragmentLogFiles: Initialize fragment logfiles (sparse/full).

  • InitialLogFileGroup: Describes log file group that is created during initial start. See documentation for format.

  • InitialNoOfOpenFiles: Initial number of files open per data node. (One thread is created per file).

  • InitialTablespace: Describes tablespace that is created during initial start. See documentation for format.

  • InsertRecoveryWork: Percentage of RecoveryWork used for inserted rows; has no effect unless partial local checkpoints are in use.

  • LateAlloc: Allocate memory after connection to management server has been established.

  • LcpScanProgressTimeout: Maximum time that local checkpoint fragment scan can be stalled before node is shut down to ensure systemwide LCP progress. Use 0 to disable.

  • LockExecuteThreadToCPU: Comma-delimited list of CPU IDs.

  • LockMaintThreadsToCPU: CPU ID indicating which CPU runs maintenance threads.

  • LockPagesInMainMemory: 0=disable locking, 1=lock after memory allocation, 2=lock before memory allocation.

  • LogLevelCheckpoint: Log level of local and global checkpoint information printed to stdout.

  • LogLevelCongestion: Level of congestion information printed to stdout.

  • LogLevelConnection: Level of node connect/disconnect information printed to stdout.

  • LogLevelError: Transporter, heartbeat errors printed to stdout.

  • LogLevelInfo: Heartbeat and log information printed to stdout.

  • LogLevelNodeRestart: Level of node restart and node failure information printed to stdout.

  • LogLevelShutdown: Level of node shutdown information printed to stdout.

  • LogLevelStartup: Level of node startup information printed to stdout.

  • LogLevelStatistic: Level of transaction, operation, and transporter information printed to stdout.

  • LongMessageBuffer: Number of bytes allocated on each data node for internal long messages.

  • MaxAllocate: Maximum size of allocation to use when allocating memory for tables.

  • MaxBufferedEpochs: Allowed numbered of epochs that subscribing node can lag behind (unprocessed epochs). Exceeding causes lagging subscribers to be disconnected.

  • MaxBufferedEpochBytes: Total number of bytes allocated for buffering epochs.

  • MaxDiskDataLatency: Maximum allowed mean latency of disk access (ms) before starting to abort transactions.

  • MaxDiskWriteSpeed: Maximum number of bytes per second that can be written by LCP and backup when no restarts are ongoing.

  • MaxDiskWriteSpeedOtherNodeRestart: Maximum number of bytes per second that can be written by LCP and backup when another node is restarting.

  • MaxDiskWriteSpeedOwnRestart: Maximum number of bytes per second that can be written by LCP and backup when this node is restarting.

  • MaxFKBuildBatchSize: Maximum scan batch size to use for building foreign keys. Increasing this value may speed up builds of foreign keys but impacts ongoing traffic as well.

  • MaxDMLOperationsPerTransaction: Limit size of transaction; aborts transaction if it requires more than this many DML operations. Set to 0 to disable.

  • MaxLCPStartDelay: Time in seconds that LCP polls for checkpoint mutex (to allow other data nodes to complete metadata synchronization), before putting itself in lock queue for parallel recovery of table data.

  • MaxNoOfAttributes: Suggests total number of attributes stored in database (sum over all tables).

  • MaxNoOfConcurrentIndexOperations: Total number of index operations that can execute simultaneously on one data node.

  • MaxNoOfConcurrentOperations: Maximum number of operation records in transaction coordinator.

  • MaxNoOfConcurrentScans: Maximum number of scans executing concurrently on data node.

  • MaxNoOfConcurrentSubOperations: Maximum number of concurrent subscriber operations.

  • MaxNoOfConcurrentTransactions: Maximum number of transactions executing concurrently on this data node, total number of transactions that can be executed concurrently is this value times number of data nodes in cluster.

  • MaxNoOfFiredTriggers: Total number of triggers that can fire simultaneously on one data node.

  • MaxNoOfLocalOperations: Maximum number of operation records defined on this data node.

  • MaxNoOfLocalScans: Maximum number of fragment scans in parallel on this data node.

  • MaxNoOfOpenFiles: Maximum number of files open per data node.(One thread is created per file).

  • MaxNoOfOrderedIndexes: Total number of ordered indexes that can be defined in system.

  • MaxNoOfSavedMessages: Maximum number of error messages to write in error log and maximum number of trace files to retain.

  • MaxNoOfSubscribers: Maximum number of subscribers (default 0 = MaxNoOfTables * 2).

  • MaxNoOfSubscriptions: Maximum number of subscriptions (default 0 = MaxNoOfTables).

  • MaxNoOfTables: Suggests total number of NDB tables stored in database.

  • MaxNoOfTriggers: Total number of triggers that can be defined in system.

  • MaxNoOfUniqueHashIndexes: Total number of unique hash indexes that can be defined in system.

  • MaxParallelCopyInstances: Number of parallel copies during node restarts. Default is 0, which uses number of LDMs on both nodes, to maximum of 16.

  • MaxParallelScansPerFragment: Maximum number of parallel scans per fragment. Once this limit is reached, scans are serialized.

  • MaxReorgBuildBatchSize: Maximum scan batch size to use for reorganization of table partitions. Increasing this value may speed up table partition reorganization but impacts ongoing traffic as well.

  • MaxStartFailRetries: Maximum retries when data node fails on startup, requires StopOnError = 0. Setting to 0 causes start attempts to continue indefinitely.

  • MaxUIBuildBatchSize: Maximum scan batch size to use for building unique keys. Increasing this value may speed up builds of unique keys but impacts ongoing traffic as well.

  • MemReportFrequency: Frequency of memory reports in seconds; 0 = report only when exceeding percentage limits.

  • MinDiskWriteSpeed: Minimum number of bytes per second that can be written by LCP and backup.

  • MinFreePct: Percentage of memory resources to keep in reserve for restarts.

  • NodeGroup: Node group to which data node belongs; used only during initial start of cluster.

  • NodeGroupTransporters: Number of transporters to use between nodes in same node group.

  • NodeId: Number uniquely identifying data node among all nodes in cluster.

  • NoOfFragmentLogFiles: Number of 16 MB redo log files in each of 4 file sets belonging to data node.

  • NoOfReplicas: Number of copies of all data in database.

  • Numa: (Linux only; requires libnuma) Controls NUMA support. Setting to 0 permits system to determine use of interleaving by data node process; 1 means that it is determined by data node.

  • ODirect: Use O_DIRECT file reads and writes when possible.

  • ODirectSyncFlag: O_DIRECT writes are treated as synchronized writes; ignored when ODirect is not enabled, InitFragmentLogFiles is set to SPARSE, or both.

  • RealtimeScheduler: When true, data node threads are scheduled as real-time threads. Default is false.

  • RecoveryWork: Percentage of storage overhead for LCP files: greater value means less work in normal operations, more work during recovery.

  • RedoBuffer: Number of bytes on each data node allocated for writing redo logs.

  • RedoOverCommitCounter: When RedoOverCommitLimit has been exceeded this many times, transactions are aborted, and operations are handled as specified by DefaultOperationRedoProblemAction.

  • RedoOverCommitLimit: Each time that flushing current redo buffer takes longer than this many seconds, number of times that this has happened is compared to RedoOverCommitCounter.

  • ReservedConcurrentIndexOperations: Number of simultaneous index operations having dedicated resources on one data node.

  • ReservedConcurrentOperations: Number of simultaneous operations having dedicated resources in transaction coordinators on one data node.

  • ReservedConcurrentScans: Number of simultaneous scans having dedicated resources on one data node.

  • ReservedConcurrentTransactions: Number of simultaneous transactions having dedicated resources on one data node.

  • ReservedFiredTriggers: Number of triggers having dedicated resources on one data node.

  • ReservedLocalScans: Number of simultaneous fragment scans having dedicated resources on one data node.

  • ReservedTransactionBufferMemory: Dynamic buffer space (in bytes) for key and attribute data allocated to each data node.

  • RestartOnErrorInsert: Control type of restart caused by inserting error (when StopOnError is enabled).

  • SchedulerExecutionTimer: Number of microseconds to execute in scheduler before sending.

  • SchedulerResponsiveness: Set NDB scheduler response optimization 0-10; higher values provide better response time but lower throughput.

  • SchedulerSpinTimer: Number of microseconds to execute in scheduler before sleeping.

  • ServerPort: Port used to set up transporter for incoming connections from API nodes.

  • SharedGlobalMemory: Total number of bytes on each data node allocated for any use.

  • SpinMethod: Determines spin method used by data node; see documentation for details.

  • StartFailRetryDelay: Delay in seconds after start failure prior to retry; requires StopOnError = 0.

  • StartFailureTimeout: Milliseconds to wait before terminating. (0=Wait forever).

  • StartNoNodeGroupTimeout: Time to wait for nodes without nodegroup before trying to start (0=forever).

  • StartPartialTimeout: Milliseconds to wait before trying to start without all nodes. (0=Wait forever).

  • StartPartitionedTimeout: Milliseconds to wait before trying to start partitioned. (0=Wait forever).

  • StartupStatusReportFrequency: Frequency of status reports during startup.

  • StopOnError: When set to 0, data node automatically restarts and recovers following node failures.

  • StringMemory: Default size of string memory (0 to 100 = % of maximum, 101+ = actual bytes).

  • TcpBind_INADDR_ANY: Bind IP_ADDR_ANY so that connections can be made from anywhere (for autogenerated connections).

  • TimeBetweenEpochs: Time between epochs (synchronization used for replication).

  • TimeBetweenEpochsTimeout: Timeout for time between epochs. Exceeding causes node shutdown.

  • TimeBetweenGlobalCheckpoints: Time between group commits of transactions to disk.

  • TimeBetweenGlobalCheckpointsTimeout: Minimum timeout for group commit of transactions to disk.

  • TimeBetweenInactiveTransactionAbortCheck: Time between checks for inactive transactions.

  • TimeBetweenLocalCheckpoints: Time between taking snapshots of database (expressed in base-2 logarithm of bytes).

  • TimeBetweenWatchDogCheck: Time between execution checks inside data node.

  • TimeBetweenWatchDogCheckInitial: Time between execution checks inside data node (early start phases when memory is allocated).

  • TotalSendBufferMemory: Total memory to use for all transporter send buffers..

  • TransactionBufferMemory: Dynamic buffer space (in bytes) for key and attribute data allocated for each data node.

  • TransactionDeadlockDetectionTimeout: Time transaction can spend executing within data node. This is time that transaction coordinator waits for each data node participating in transaction to execute request. If data node takes more than this amount of time, transaction is aborted.

  • TransactionInactiveTimeout: Milliseconds that application waits before executing another part of transaction. This is time transaction coordinator waits for application to execute or send another part (query, statement) of transaction. If application takes too much time, then transaction is aborted. Timeout = 0 means that application never times out.

  • TransactionMemory: Memory allocated for transactions on each data node.

  • TwoPassInitialNodeRestartCopy: Copy data in 2 passes during initial node restart, which enables multithreaded building of ordered indexes for such restarts.

  • UndoDataBuffer: Number of bytes on each data node allocated for writing data undo logs.

  • UndoIndexBuffer: Number of bytes on each data node allocated for writing index undo logs.

  • UseShm: Use shared memory connections between this data node and API node also running on this host.

The following parameters are specific to ndbmtd:

  • AutomaticThreadConfig: Use automatic thread configuration; overrides any settings for ThreadConfig and MaxNoOfExecutionThreads.

  • ClassicFragmentation: When true, use traditional table fragmentation; set false to enable flexible distribution of table fragments among LDMs.

  • MaxNoOfExecutionThreads: For ndbmtd only, specify maximum number of execution threads.

  • NoOfFragmentLogParts: Number of redo log file groups belonging to this data node.

  • NumCPUs: Specify number of CPUs to use with AutomaticThreadConfig.

  • PartitionsPerNode: Determines the number of table partitions created on each data node; not used if ClassicFragmentation is enabled.

  • ThreadConfig: Used for configuration of multithreaded data nodes (ndbmtd). Default is empty string; see documentation for syntax and other information.

23.3.2.2 NDB Cluster Management Node Configuration Parameters

The listing in this section provides information about parameters used in the [ndb_mgmd] or [mgm] section of a config.ini file for configuring NDB Cluster management nodes. For detailed descriptions and other additional information about each of these parameters, see Section 23.3.3.5, “Defining an NDB Cluster Management Server”.

  • ArbitrationDelay: When asked to arbitrate, arbitrator waits this long before voting (milliseconds).

  • ArbitrationRank: If 0, then management node is not arbitrator. Kernel selects arbitrators in order 1, 2.

  • DataDir: Data directory for this node.

  • ExecuteOnComputer: String referencing earlier defined COMPUTER.

  • ExtraSendBufferMemory: Memory to use for send buffers in addition to any allocated by TotalSendBufferMemory or SendBufferMemory. Default (0) allows up to 16MB.

  • HeartbeatIntervalMgmdMgmd: Time between management-node-to-management-node heartbeats; connection between management nodes is considered lost after 3 missed heartbeats.

  • HeartbeatThreadPriority: Set heartbeat thread policy and priority for management nodes; see manual for allowed values.

  • HostName: Host name or IP address for this management node.

  • Id: Number identifying management node. Now deprecated; use NodeId instead.

  • LogDestination: Where to send log messages: console, system log, or specified log file.

  • NodeId: Number uniquely identifying management node among all nodes in cluster.

  • PortNumber: Port number to send commands to and fetch configuration from management server.

  • PortNumberStats: Port number used to get statistical information from management server.

  • TotalSendBufferMemory: Total memory to use for all transporter send buffers.

  • wan: Use WAN TCP setting as default.

Note

After making changes in a management node's configuration, it is necessary to perform a rolling restart of the cluster for the new configuration to take effect. See Section 23.3.3.5, “Defining an NDB Cluster Management Server”, for more information.

To add new management servers to a running NDB Cluster, it is also necessary perform a rolling restart of all cluster nodes after modifying any existing config.ini files. For more information about issues arising when using multiple management nodes, see Section 23.1.7.10, “Limitations Relating to Multiple NDB Cluster Nodes”.

23.3.2.3 NDB Cluster SQL Node and API Node Configuration Parameters

The listing in this section provides information about parameters used in the [mysqld] and [api] sections of a config.ini file for configuring NDB Cluster SQL nodes and API nodes. For detailed descriptions and other additional information about each of these parameters, see Section 23.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”.

  • ApiVerbose: Enable NDB API debugging; for NDB development.

  • ArbitrationDelay: When asked to arbitrate, arbitrator waits this many milliseconds before voting.

  • ArbitrationRank: If 0, then API node is not arbitrator. Kernel selects arbitrators in order 1, 2.

  • AutoReconnect: Specifies whether an API node should reconnect fully when disconnected from cluster.

  • BatchByteSize: Default batch size in bytes.

  • BatchSize: Default batch size in number of records.

  • ConnectBackoffMaxTime: Specifies longest time in milliseconds (~100ms resolution) to allow between connection attempts to any given data node by this API node. Excludes time elapsed while connection attempts are ongoing, which in worst case can take several seconds. Disable by setting to 0. If no data nodes are currently connected to this API node, StartConnectBackoffMaxTime is used instead.

  • ConnectionMap: Specifies which data nodes to connect.

  • DefaultHashMapSize: Set size (in buckets) to use for table hash maps. Three values are supported: 0, 240, and 3840.

  • DefaultOperationRedoProblemAction: How operations are handled in event that RedoOverCommitCounter is exceeded.

  • ExecuteOnComputer: String referencing earlier defined COMPUTER.

  • ExtraSendBufferMemory: Memory to use for send buffers in addition to any allocated by TotalSendBufferMemory or SendBufferMemory. Default (0) allows up to 16MB.

  • HeartbeatThreadPriority: Set heartbeat thread policy and priority for API nodes; see manual for allowed values.

  • HostName: Host name or IP address for this SQL or API node.

  • Id: Number identifying MySQL server or API node (Id). Now deprecated; use NodeId instead.

  • MaxScanBatchSize: Maximum collective batch size for one scan.

  • NodeId: Number uniquely identifying SQL node or API node among all nodes in cluster.

  • StartConnectBackoffMaxTime: Same as ConnectBackoffMaxTime except that this parameter is used in its place if no data nodes are connected to this API node.

  • TotalSendBufferMemory: Total memory to use for all transporter send buffers.

  • wan: Use WAN TCP setting as default.

For a discussion of MySQL server options for NDB Cluster, see Section 23.3.3.9.1, “MySQL Server Options for NDB Cluster”. For information about MySQL server system variables relating to NDB Cluster, see Section 23.3.3.9.2, “NDB Cluster System Variables”.

Note

To add new SQL or API nodes to the configuration of a running NDB Cluster, it is necessary to perform a rolling restart of all cluster nodes after adding new [mysqld] or [api] sections to the config.ini file (or files, if you are using more than one management server). This must be done before the new SQL or API nodes can connect to the cluster.

It is not necessary to perform any restart of the cluster if new SQL or API nodes can employ previously unused API slots in the cluster configuration to connect to the cluster.

23.3.2.4 Other NDB Cluster Configuration Parameters

The listings in this section provide information about parameters used in the [computer], [tcp], and [shm] sections of a config.ini file for configuring NDB Cluster. For detailed descriptions and additional information about individual parameters, see Section 23.3.3.10, “NDB Cluster TCP/IP Connections”, or Section 23.3.3.12, “NDB Cluster Shared-Memory Connections”, as appropriate.

The following parameters apply to the config.ini file's [computer] section:

  • HostName: Host name or IP address of this computer.

  • Id: Unique identifier for this computer.

The following parameters apply to the config.ini file's [tcp] section:

  • AllowUnresolvedHostNames: When false (default), failure by management node to resolve host name results in fatal error; when true, unresolved host names are reported as warnings only.

  • Checksum: If checksum is enabled, all signals between nodes are checked for errors.

  • Group: Used for group proximity; smaller value is interpreted as being closer.

  • NodeId1: ID of node (data node, API node, or management node) on one side of connection.

  • NodeId2: ID of node (data node, API node, or management node) on one side of connection.

  • NodeIdServer: Set server side of TCP connection.

  • OverloadLimit: When more than this many unsent bytes are in send buffer, connection is considered overloaded.

  • PreSendChecksum: If this parameter and Checksum are both enabled, perform pre-send checksum checks, and check all TCP signals between nodes for errors.

  • Proxy: .

  • ReceiveBufferMemory: Bytes of buffer for signals received by this node.

  • SendBufferMemory: Bytes of TCP buffer for signals sent from this node.

  • SendSignalId: Sends ID in each signal. Used in trace files. Defaults to true in debug builds.

  • TCP_MAXSEG_SIZE: Value used for TCP_MAXSEG.

  • TCP_RCV_BUF_SIZE: Value used for SO_RCVBUF.

  • TCP_SND_BUF_SIZE: Value used for SO_SNDBUF.

  • TcpBind_INADDR_ANY: Bind InAddrAny instead of host name for server part of connection.

The following parameters apply to the config.ini file's [shm] section:

  • Checksum: If checksum is enabled, all signals between nodes are checked for errors.

  • Group: Used for group proximity; smaller value is interpreted as being closer.

  • NodeId1: ID of node (data node, API node, or management node) on one side of connection.

  • NodeId2: ID of node (data node, API node, or management node) on one side of connection.

  • NodeIdServer: Set server side of SHM connection.

  • OverloadLimit: When more than this many unsent bytes are in send buffer, connection is considered overloaded.

  • PreSendChecksum: If this parameter and Checksum are both enabled, perform pre-send checksum checks, and check all SHM signals between nodes for errors.

  • SendBufferMemory: Bytes in shared memory buffer for signals sent from this node.

  • SendSignalId: Sends ID in each signal. Used in trace files.

  • ShmKey: Shared memory key; when set to 1, this is calculated by NDB.

  • ShmSpinTime: When receiving, number of microseconds to spin before sleeping.

  • ShmSize: Size of shared memory segment.

  • Signum: Signal number to be used for signalling.

23.3.2.5 NDB Cluster mysqld Option and Variable Reference

The following table provides a list of the command-line options, server and status variables applicable within mysqld when it is running as an SQL node in an NDB Cluster. For a table showing all command-line options, server and status variables available for use with mysqld, see Section 5.1.4, “Server Option, System Variable, and Status Variable Reference”.

23.3.3 NDB Cluster Configuration Files

Configuring NDB Cluster requires working with two files:

  • my.cnf: Specifies options for all NDB Cluster executables. This file, with which you should be familiar with from previous work with MySQL, must be accessible by each executable running in the cluster.

  • config.ini: This file, sometimes known as the global configuration file, is read only by the NDB Cluster management server, which then distributes the information contained therein to all processes participating in the cluster. config.ini contains a description of each node involved in the cluster. This includes configuration parameters for data nodes and configuration parameters for connections between all nodes in the cluster. For a quick reference to the sections that can appear in this file, and what sorts of configuration parameters may be placed in each section, see Sections of the config.ini File.

Caching of configuration data.  NDB uses stateful configuration. Rather than reading the global configuration file every time the management server is restarted, the management server caches the configuration the first time it is started, and thereafter, the global configuration file is read only when one of the following conditions is true:

  • The management server is started using the --initial option.  When --initial is used, the global configuration file is re-read, any existing cache files are deleted, and the management server creates a new configuration cache.

  • The management server is started using the --reload option.  The --reload option causes the management server to compare its cache with the global configuration file. If they differ, the management server creates a new configuration cache; any existing configuration cache is preserved, but not used. If the management server's cache and the global configuration file contain the same configuration data, then the existing cache is used, and no new cache is created.

  • The management server is started using --config-cache=FALSE.  This disables --config-cache (enabled by default), and can be used to force the management server to bypass configuration caching altogether. In this case, the management server ignores any configuration files that may be present, always reading its configuration data from the config.ini file instead.

  • No configuration cache is found.  In this case, the management server reads the global configuration file and creates a cache containing the same configuration data as found in the file.

Configuration cache files.  The management server by default creates configuration cache files in a directory named mysql-cluster in the MySQL installation directory. (If you build NDB Cluster from source on a Unix system, the default location is /usr/local/mysql-cluster.) This can be overridden at runtime by starting the management server with the --configdir option. Configuration cache files are binary files named according to the pattern ndb_node_id_config.bin.seq_id, where node_id is the management server's node ID in the cluster, and seq_id is a cache idenitifer. Cache files are numbered sequentially using seq_id, in the order in which they are created. The management server uses the latest cache file as determined by the seq_id.

Note

It is possible to roll back to a previous configuration by deleting later configuration cache files, or by renaming an earlier cache file so that it has a higher seq_id. However, since configuration cache files are written in a binary format, you should not attempt to edit their contents by hand.

For more information about the --configdir, --config-cache, --initial, and --reload options for the NDB Cluster management server, see Section 23.4.4, “ndb_mgmd — The NDB Cluster Management Server Daemon”.

We are continuously making improvements in NDB Cluster configuration and attempting to simplify this process. Although we strive to maintain backward compatibility, there may be times when introduce an incompatible change. In such cases we try to let NDB Cluster users know in advance if a change is not backward compatible. If you find such a change and we have not documented it, please report it in the MySQL bugs database using the instructions given in Section 1.6, “How to Report Bugs or Problems”.

23.3.3.1 NDB Cluster Configuration: Basic Example

To support NDB Cluster, you should update my.cnf as shown in the following example. You may also specify these parameters on the command line when invoking the executables.

Note

The options shown here should not be confused with those that are used in config.ini global configuration files. Global configuration options are discussed later in this section.

# my.cnf
# example additions to my.cnf for NDB Cluster
# (valid in MySQL 8.0)

# enable ndbcluster storage engine, and provide connection string for
# management server host (default port is 1186)
[mysqld]
ndbcluster
ndb-connectstring=ndb_mgmd.mysql.com


# provide connection string for management server host (default port: 1186)
[ndbd]
connect-string=ndb_mgmd.mysql.com

# provide connection string for management server host (default port: 1186)
[ndb_mgm]
connect-string=ndb_mgmd.mysql.com

# provide location of cluster configuration file
[ndb_mgmd]
config-file=/etc/config.ini

(For more information on connection strings, see Section 23.3.3.3, “NDB Cluster Connection Strings”.)

# my.cnf
# example additions to my.cnf for NDB Cluster
# (works on all versions)

# enable ndbcluster storage engine, and provide connection string for management
# server host to the default port 1186
[mysqld]
ndbcluster
ndb-connectstring=ndb_mgmd.mysql.com:1186
Important

Once you have started a mysqld process with the NDBCLUSTER and ndb-connectstring parameters in the [mysqld] in the my.cnf file as shown previously, you cannot execute any CREATE TABLE or ALTER TABLE statements without having actually started the cluster. Otherwise, these statements fail with an error. This is by design.

You may also use a separate [mysql_cluster] section in the cluster my.cnf file for settings to be read and used by all executables:

# cluster-specific settings
[mysql_cluster]
ndb-connectstring=ndb_mgmd.mysql.com:1186

For additional NDB variables that can be set in the my.cnf file, see Section 23.3.3.9.2, “NDB Cluster System Variables”.

The NDB Cluster global configuration file is by convention named config.ini (but this is not required). If needed, it is read by ndb_mgmd at startup and can be placed in any location that can be read by it. The location and name of the configuration are specified using --config-file=path_name with ndb_mgmd on the command line. This option has no default value, and is ignored if ndb_mgmd uses the configuration cache.

The global configuration file for NDB Cluster uses INI format, which consists of sections preceded by section headings (surrounded by square brackets), followed by the appropriate parameter names and values. One deviation from the standard INI format is that the parameter name and value can be separated by a colon (:) as well as the equal sign (=); however, the equal sign is preferred. Another deviation is that sections are not uniquely identified by section name. Instead, unique sections (such as two different nodes of the same type) are identified by a unique ID specified as a parameter within the section.

Default values are defined for most parameters, and can also be specified in config.ini. To create a default value section, simply add the word default to the section name. For example, an [ndbd] section contains parameters that apply to a particular data node, whereas an [ndbd default] section contains parameters that apply to all data nodes. Suppose that all data nodes should use the same data memory size. To configure them all, create an [ndbd default] section that contains a DataMemory line to specify the data memory size.

If used, the [ndbd default] section must precede any [ndbd] sections in the configuration file. This is also true for default sections of any other type.

Note

In some older releases of NDB Cluster, there was no default value for NoOfReplicas, which always had to be specified explicitly in the [ndbd default] section. Although this parameter now has a default value of 2, which is the recommended setting in most common usage scenarios, it is still recommended practice to set this parameter explicitly.

The global configuration file must define the computers and nodes involved in the cluster and on which computers these nodes are located. An example of a simple configuration file for a cluster consisting of one management server, two data nodes and two MySQL servers is shown here:

# file "config.ini" - 2 data nodes and 2 SQL nodes
# This file is placed in the startup directory of ndb_mgmd (the
# management server)
# The first MySQL Server can be started from any host. The second
# can be started only on the host mysqld_5.mysql.com

[ndbd default]
NoOfReplicas= 2
DataDir= /var/lib/mysql-cluster

[ndb_mgmd]
Hostname= ndb_mgmd.mysql.com
DataDir= /var/lib/mysql-cluster

[ndbd]
HostName= ndbd_2.mysql.com

[ndbd]
HostName= ndbd_3.mysql.com

[mysqld]
[mysqld]
HostName= mysqld_5.mysql.com
Note

The preceding example is intended as a minimal starting configuration for purposes of familiarization with NDB Cluster , and is almost certain not to be sufficient for production settings. See Section 23.3.3.2, “Recommended Starting Configuration for NDB Cluster”, which provides a more complete example starting configuration.

Each node has its own section in the config.ini file. For example, this cluster has two data nodes, so the preceding configuration file contains two [ndbd] sections defining these nodes.

Note

Do not place comments on the same line as a section heading in the config.ini file; this causes the management server not to start because it cannot parse the configuration file in such cases.

Sections of the config.ini File

There are six different sections that you can use in the config.ini configuration file, as described in the following list:

You can define default values for each section. If used, a default section should come before any other sections of that type. For example, an [ndbd default] section should appear in the configuration file before any [ndbd] sections.

NDB Cluster parameter names are case-insensitive, unless specified in MySQL Server my.cnf or my.ini files.

23.3.3.2 Recommended Starting Configuration for NDB Cluster

Achieving the best performance from an NDB Cluster depends on a number of factors including the following:

  • NDB Cluster software version

  • Numbers of data nodes and SQL nodes

  • Hardware

  • Operating system

  • Amount of data to be stored

  • Size and type of load under which the cluster is to operate

Therefore, obtaining an optimum configuration is likely to be an iterative process, the outcome of which can vary widely with the specifics of each NDB Cluster deployment. Changes in configuration are also likely to be indicated when changes are made in the platform on which the cluster is run, or in applications that use the NDB Cluster 's data. For these reasons, it is not possible to offer a single configuration that is ideal for all usage scenarios. However, in this section, we provide a recommended base configuration.

Starting config.ini file.  The following config.ini file is a recommended starting point for configuring a cluster running NDB Cluster 8.0:

# TCP PARAMETERS

[tcp default]
SendBufferMemory=2M
ReceiveBufferMemory=2M

# Increasing the sizes of these 2 buffers beyond the default values
# helps prevent bottlenecks due to slow disk I/O.

# MANAGEMENT NODE PARAMETERS

[ndb_mgmd default]
DataDir=path/to/management/server/data/directory

# It is possible to use a different data directory for each management
# server, but for ease of administration it is preferable to be
# consistent.

[ndb_mgmd]
HostName=management-server-A-hostname
# NodeId=management-server-A-nodeid

[ndb_mgmd]
HostName=management-server-B-hostname
# NodeId=management-server-B-nodeid

# Using 2 management servers helps guarantee that there is always an
# arbitrator in the event of network partitioning, and so is
# recommended for high availability. Each management server must be
# identified by a HostName. You may for the sake of convenience specify
# a NodeId for any management server, although one is allocated
# for it automatically; if you do so, it must be in the range 1-255
# inclusive and must be unique among all IDs specified for cluster
# nodes.

# DATA NODE PARAMETERS

[ndbd default]
NoOfReplicas=2

# Using two fragment replicas is recommended to guarantee availability of data;
# using only one fragment replica does not provide any redundancy, which means
# that the failure of a single data node causes the entire cluster to
# shut down. As of NDB 8.0.19, it is also possible (but not required) to
# use more than two fragment replicas, although two fragment replicas are
# sufficient to provide high availability.

LockPagesInMainMemory=1

# On Linux and Solaris systems, setting this parameter locks data node
# processes into memory. Doing so prevents them from swapping to disk,
# which can severely degrade cluster performance.

DataMemory=3456M

# The value provided for DataMemory assumes 4 GB RAM
# per data node. However, for best results, you should first calculate
# the memory that would be used based on the data you actually plan to
# store (you may find the ndb_size.pl utility helpful in estimating
# this), then allow an extra 20% over the calculated values. Naturally,
# you should ensure that each data node host has at least as much
# physical memory as the sum of these two values.

# ODirect=1

# Enabling this parameter causes NDBCLUSTER to try using O_DIRECT
# writes for local checkpoints and redo logs; this can reduce load on
# CPUs. We recommend doing so when using NDB Cluster on systems running
# Linux kernel 2.6 or later.

NoOfFragmentLogFiles=300
DataDir=path/to/data/node/data/directory
MaxNoOfConcurrentOperations=100000

SchedulerSpinTimer=400
SchedulerExecutionTimer=100
RealTimeScheduler=1
# Setting these parameters allows you to take advantage of real-time scheduling
# of NDB threads to achieve increased throughput when using ndbd. They
# are not needed when using ndbmtd; in particular, you should not set
# RealTimeScheduler for ndbmtd data nodes.

TimeBetweenGlobalCheckpoints=1000
TimeBetweenEpochs=200
RedoBuffer=32M

# CompressedLCP=1
# CompressedBackup=1
# Enabling CompressedLCP and CompressedBackup causes, respectively, local
checkpoint files and backup files to be compressed, which can result in a space
savings of up to 50% over noncompressed LCPs and backups.

# MaxNoOfLocalScans=64
MaxNoOfTables=1024
MaxNoOfOrderedIndexes=256

[ndbd]
HostName=data-node-A-hostname
# NodeId=data-node-A-nodeid

LockExecuteThreadToCPU=1
LockMaintThreadsToCPU=0
# On systems with multiple CPUs, these parameters can be used to lock NDBCLUSTER
# threads to specific CPUs

[ndbd]
HostName=data-node-B-hostname
# NodeId=data-node-B-nodeid

LockExecuteThreadToCPU=1
LockMaintThreadsToCPU=0

# You must have an [ndbd] section for every data node in the cluster;
# each of these sections must include a HostName. Each section may
# optionally include a NodeId for convenience, but in most cases, it is
# sufficient to allow the cluster to allocate node IDs dynamically. If
# you do specify the node ID for a data node, it must be in the range 1
# to 144 inclusive and must be unique among all IDs specified for
# cluster nodes. (Previous to NDB 8.0.18, this range was 1 to 48 inclusive.)

# SQL NODE / API NODE PARAMETERS

[mysqld]
# HostName=sql-node-A-hostname
# NodeId=sql-node-A-nodeid

[mysqld]

[mysqld]

# Each API or SQL node that connects to the cluster requires a [mysqld]
# or [api] section of its own. Each such section defines a connection
# slot; you should have at least as many of these sections in the
# config.ini file as the total number of API nodes and SQL nodes that
# you wish to have connected to the cluster at any given time. There is
# no performance or other penalty for having extra slots available in
# case you find later that you want or need more API or SQL nodes to
# connect to the cluster at the same time.
# If no HostName is specified for a given [mysqld] or [api] section,
# then any API or SQL node may use that slot to connect to the
# cluster. You may wish to use an explicit HostName for one connection slot
# to guarantee that an API or SQL node from that host can always
# connect to the cluster. If you wish to prevent API or SQL nodes from
# connecting from other than a desired host or hosts, then use a
# HostName for every [mysqld] or [api] section in the config.ini file.
# You can if you wish define a node ID (NodeId parameter) for any API or
# SQL node, but this is not necessary; if you do so, it must be in the
# range 1 to 255 inclusive and must be unique among all IDs specified
# for cluster nodes.

Recommended my.cnf options for SQL nodes.  MySQL Servers acting as NDB Cluster SQL nodes must always be started with the --ndbcluster and --ndb-connectstring options, either on the command line or in my.cnf. In addition, set the following options for all mysqld processes in the cluster, unless your setup requires otherwise:

  • --ndb-use-exact-count=0

  • --ndb-index-stat-enable=0

  • --ndb-force-send=1

  • --optimizer-switch=engine_condition_pushdown=on

23.3.3.3 NDB Cluster Connection Strings

With the exception of the NDB Cluster management server (ndb_mgmd), each node that is part of an NDB Cluster requires a connection string that points to the management server's location. This connection string is used in establishing a connection to the management server as well as in performing other tasks depending on the node's role in the cluster. The syntax for a connection string is as follows:

[nodeid=node_id, ]host-definition[, host-definition[, ...]]

host-definition:
    host_name[:port_number]

node_id is an integer greater than or equal to 1 which identifies a node in config.ini. host_name is a string representing a valid Internet host name or IP address. port_number is an integer referring to a TCP/IP port number.

example 1 (long):    "nodeid=2,myhost1:1100,myhost2:1100,198.51.100.3:1200"
example 2 (short):   "myhost1"

localhost:1186 is used as the default connection string value if none is provided. If port_num is omitted from the connection string, the default port is 1186. This port should always be available on the network because it has been assigned by IANA for this purpose (see http://www.iana.org/assignments/port-numbers for details).

By listing multiple host definitions, it is possible to designate several redundant management servers. An NDB Cluster data or API node attempts to contact successive management servers on each host in the order specified, until a successful connection has been established.

It is also possible to specify in a connection string one or more bind addresses to be used by nodes having multiple network interfaces for connecting to management servers. A bind address consists of a hostname or network address and an optional port number. This enhanced syntax for connection strings is shown here:

[nodeid=node_id, ]
    [bind-address=host-definition, ]
    host-definition[; bind-address=host-definition]
    host-definition[; bind-address=host-definition]
    [, ...]]

host-definition:
    host_name[:port_number]

If a single bind address is used in the connection string prior to specifying any management hosts, then this address is used as the default for connecting to any of them (unless overridden for a given management server; see later in this section for an example). For example, the following connection string causes the node to use 198.51.100.242 regardless of the management server to which it connects:

bind-address=198.51.100.242, poseidon:1186, perch:1186

If a bind address is specified following a management host definition, then it is used only for connecting to that management node. Consider the following connection string:

poseidon:1186;bind-address=localhost, perch:1186;bind-address=198.51.100.242

In this case, the node uses localhost to connect to the management server running on the host named poseidon and 198.51.100.242 to connect to the management server running on the host named perch.

You can specify a default bind address and then override this default for one or more specific management hosts. In the following example, localhost is used for connecting to the management server running on host poseidon; since 198.51.100.242 is specified first (before any management server definitions), it is the default bind address and so is used for connecting to the management servers on hosts perch and orca:

bind-address=198.51.100.242,poseidon:1186;bind-address=localhost,perch:1186,orca:2200

There are a number of different ways to specify the connection string:

  • Each executable has its own command-line option which enables specifying the management server at startup. (See the documentation for the respective executable.)

  • It is also possible to set the connection string for all nodes in the cluster at once by placing it in a [mysql_cluster] section in the management server's my.cnf file.

  • For backward compatibility, two other options are available, using the same syntax:

    1. Set the NDB_CONNECTSTRING environment variable to contain the connection string.

    2. Write the connection string for each executable into a text file named Ndb.cfg and place this file in the executable's startup directory.

    However, these are now deprecated and should not be used for new installations.

The recommended method for specifying the connection string is to set it on the command line or in the my.cnf file for each executable.

23.3.3.4 Defining Computers in an NDB Cluster

The [computer] section has no real significance other than serving as a way to avoid the need of defining host names for each node in the system. All parameters mentioned here are required.

  • Id

    Version (or later) NDB 8.0.13
    Type or units string
    Default [none]
    Range ...
    Restart Type IS

    This is a unique identifier, used to refer to the host computer elsewhere in the configuration file.

    Important

    The computer ID is not the same as the node ID used for a management, API, or data node. Unlike the case with node IDs, you cannot use NodeId in place of Id in the [computer] section of the config.ini file.

  • HostName

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    This is the computer's hostname or IP address.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.8 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.5 Defining an NDB Cluster Management Server

The [ndb_mgmd] section is used to configure the behavior of the management server. If multiple management servers are employed, you can specify parameters common to all of them in an [ndb_mgmd default] section. [mgm] and [mgm default] are older aliases for these, supported for backward compatibility.

All parameters in the following list are optional and assume their default values if omitted.

Note

If neither the ExecuteOnComputer nor the HostName parameter is present, the default value localhost is assumed for both.

  • Id

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 255
    Restart Type IS

    Each node in the cluster has a unique identity. For a management node, this is represented by an integer value in the range 1 to 255, inclusive. This ID is used by all internal cluster messages for addressing the node, and so must be unique for each NDB Cluster node, regardless of the type of node.

    Note

    Data node IDs must be less than 145. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for management nodes (and API nodes) to values greater than 144. (In NDB 8.0.17 and earlier, the maximum value for a data node ID was 48.)

    The use of the Id parameter for identifying management nodes is deprecated in favor of NodeId. Although Id continues to be supported for backward compatibility, it now generates a warning and is subject to removal in a future version of NDB Cluster.

  • NodeId

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 255
    Restart Type IS

    Each node in the cluster has a unique identity. For a management node, this is represented by an integer value in the range 1 to 255 inclusive. This ID is used by all internal cluster messages for addressing the node, and so must be unique for each NDB Cluster node, regardless of the type of node.

    Note

    As of NDB 8.0.18, data node IDs must be less than 145. (Previously, this was less than 49.) If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for management nodes (and API nodes) to values greater than 144.

    NodeId is the preferred parameter name to use when identifying management nodes. Although the older Id continues to be supported for backward compatibility, it is now deprecated and generates a warning when used; it is also subject to removal in a future NDB Cluster release.

  • ExecuteOnComputer

    Version (or later) NDB 8.0.13
    Type or units name
    Default [none]
    Range ...
    Restart Type S
    Deprecated Yes (in NDB 7.5)

    This refers to the Id set for one of the computers defined in a [computer] section of the config.ini file.

    Important

    This parameter is deprecated, and is subject to removal in a future release. Use the HostName parameter instead.

  • PortNumber

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 1186
    Range 0 - 64K
    Restart Type S

    This is the port number on which the management server listens for configuration requests and management commands.

  • The node ID for this node can be given out only to connections that explicitly request it. A management server that requests any node ID cannot use this one. This parameter can be used when running multiple management servers on the same host, and HostName is not sufficient for distinguishing among processes. Intended for use in testing.

  • HostName

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    Specifying this parameter defines the hostname of the computer on which the management node is to reside. To specify a hostname other than localhost, either this parameter or ExecuteOnComputer is required.

  • LocationDomainId

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 16
    Restart Type S

    Assigns a management node to a specific availability domain (also known as an availability zone) within a cloud. By informing NDB which nodes are in which availability domains, performance can be improved in a cloud environment in the following ways:

    • If requested data is not found on the same node, reads can be directed to another node in the same availability domain.

    • Communication between nodes in different availability domains are guaranteed to use NDB transporters' WAN support without any further manual intervention.

    • The transporter's group number can be based on which availability domain is used, such that also SQL and other API nodes communicate with local data nodes in the same availability domain whenever possible.

    • The arbitrator can be selected from an availability domain in which no data nodes are present, or, if no such availability domain can be found, from a third availability domain.

    LocationDomainId takes an integer value between 0 and 16 inclusive, with 0 being the default; using 0 is the same as leaving the parameter unset.

  • LogDestination

    Version (or later) NDB 8.0.13
    Type or units {CONSOLE|SYSLOG|FILE}
    Default FILE: filename=ndb_nodeid_cluster.log, maxsize=1000000, maxfiles=6
    Range ...
    Restart Type N

    This parameter specifies where to send cluster logging information. There are three options in this regard—CONSOLE, SYSLOG, and FILE—with FILE being the default:

    • CONSOLE outputs the log to stdout:

      CONSOLE
      
    • SYSLOG sends the log to a syslog facility, possible values being one of auth, authpriv, cron, daemon, ftp, kern, lpr, mail, news, syslog, user, uucp, local0, local1, local2, local3, local4, local5, local6, or local7.

      Note

      Not every facility is necessarily supported by every operating system.

      SYSLOG:facility=syslog
      
    • FILE pipes the cluster log output to a regular file on the same machine. The following values can be specified:

      • filename: The name of the log file.

        The default log file name used in such cases is ndb_nodeid_cluster.log.

      • maxsize: The maximum size (in bytes) to which the file can grow before logging rolls over to a new file. When this occurs, the old log file is renamed by appending .N to the file name, where N is the next number not yet used with this name.

      • maxfiles: The maximum number of log files.

      FILE:filename=cluster.log,maxsize=1000000,maxfiles=6
      

      The default value for the FILE parameter is FILE:filename=ndb_node_id_cluster.log,maxsize=1000000,maxfiles=6, where node_id is the ID of the node.

    It is possible to specify multiple log destinations separated by semicolons as shown here:

    CONSOLE;SYSLOG:facility=local0;FILE:filename=/var/log/mgmd
    
  • ArbitrationRank

    Version (or later) NDB 8.0.13
    Type or units 0-2
    Default 1
    Range 0 - 2
    Restart Type N

    This parameter is used to define which nodes can act as arbitrators. Only management nodes and SQL nodes can be arbitrators. ArbitrationRank can take one of the following values:

    • 0: The node is never used as an arbitrator.

    • 1: The node has high priority; that is, it is preferred as an arbitrator over low-priority nodes.

    • 2: Indicates a low-priority node which is used as an arbitrator only if a node with a higher priority is not available for that purpose.

    Normally, the management server should be configured as an arbitrator by setting its ArbitrationRank to 1 (the default for management nodes) and those for all SQL nodes to 0 (the default for SQL nodes).

    You can disable arbitration completely either by setting ArbitrationRank to 0 on all management and SQL nodes, or by setting the Arbitration parameter in the [ndbd default] section of the config.ini global configuration file. Setting Arbitration causes any settings for ArbitrationRank to be disregarded.

  • ArbitrationDelay

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    An integer value which causes the management server's responses to arbitration requests to be delayed by that number of milliseconds. By default, this value is 0; it is normally not necessary to change it.

  • DataDir

    Version (or later) NDB 8.0.13
    Type or units path
    Default .
    Range ...
    Restart Type N

    This specifies the directory where output files from the management server are placed. These files include cluster log files, process output files, and the daemon's process ID (PID) file. (For log files, this location can be overridden by setting the FILE parameter for LogDestination, as discussed previously in this section.)

    The default value for this parameter is the directory in which ndb_mgmd is located.

  • PortNumberStats

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 0 - 64K
    Restart Type N

    This parameter specifies the port number used to obtain statistical information from an NDB Cluster management server. It has no default value.

  • Wan

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Use WAN TCP setting as default.

  • HeartbeatThreadPriority

    Version (or later) NDB 8.0.13
    Type or units string
    Default [none]
    Range ...
    Restart Type S

    Set the scheduling policy and priority of heartbeat threads for management and API nodes.

    The syntax for setting this parameter is shown here:

    HeartbeatThreadPriority = policy[, priority]
    
    policy:
      {FIFO | RR}
    

    When setting this parameter, you must specify a policy. This is one of FIFO (first in, first out) or RR (round robin). The policy value is followed optionally by the priority (an integer).

  • ExtraSendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 0 - 32G
    Restart Type N

    This parameter specifies the amount of transporter send buffer memory to allocate in addition to any that has been set using TotalSendBufferMemory, SendBufferMemory, or both.

  • TotalSendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 256K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter is used to determine the total amount of memory to allocate on this node for shared send buffer memory among all configured transporters.

    If this parameter is set, its minimum permitted value is 256KB; 0 indicates that the parameter has not been set. For more detailed information, see Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”.

  • HeartbeatIntervalMgmdMgmd

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 1500
    Range 100 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Specify the interval between heartbeat messages used to determine whether another management node is on contact with this one. The management node waits after 3 of these intervals to declare the connection dead; thus, the default setting of 1500 milliseconds causes the management node to wait for approximately 1600 ms before timing out.

Note

After making changes in a management node's configuration, it is necessary to perform a rolling restart of the cluster for the new configuration to take effect.

To add new management servers to a running NDB Cluster, it is also necessary to perform a rolling restart of all cluster nodes after modifying any existing config.ini files. For more information about issues arising when using multiple management nodes, see Section 23.1.7.10, “Limitations Relating to Multiple NDB Cluster Nodes”.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.9 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.6 Defining NDB Cluster Data Nodes

The [ndbd] and [ndbd default] sections are used to configure the behavior of the cluster's data nodes.

[ndbd] and [ndbd default] are always used as the section names whether you are using ndbd or ndbmtd binaries for the data node processes.

There are many parameters which control buffer sizes, pool sizes, timeouts, and so forth. The only mandatory parameter is either one of ExecuteOnComputer or HostName; this must be defined in the local [ndbd] section.

The parameter NoOfReplicas should be defined in the [ndbd default] section, as it is common to all Cluster data nodes. It is not strictly necessary to set NoOfReplicas, but it is good practice to set it explicitly.

Most data node parameters are set in the [ndbd default] section. Only those parameters explicitly stated as being able to set local values are permitted to be changed in the [ndbd] section. Where present, HostName, NodeId and ExecuteOnComputer must be defined in the local [ndbd] section, and not in any other section of config.ini. In other words, settings for these parameters are specific to one data node.

For those parameters affecting memory usage or buffer sizes, it is possible to use K, M, or G as a suffix to indicate units of 1024, 1024×1024, or 1024×1024×1024. (For example, 100K means 100 × 1024 = 102400.)

Parameter names and values are case-insensitive, unless used in a MySQL Server my.cnf or my.ini file, in which case they are case-sensitive.

Information about configuration parameters specific to NDB Cluster Disk Data tables can be found later in this section (see Disk Data Configuration Parameters).

All of these parameters also apply to ndbmtd (the multithreaded version of ndbd). Three additional data node configuration parameters—MaxNoOfExecutionThreads, ThreadConfig, and NoOfFragmentLogParts—apply to ndbmtd only; these have no effect when used with ndbd. For more information, see Multi-Threading Configuration Parameters (ndbmtd). See also Section 23.4.3, “ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)”.

Identifying data nodes.  The NodeId or Id value (that is, the data node identifier) can be allocated on the command line when the node is started or in the configuration file.

  • NodeId

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 48
    Restart Type IS
    Version (or later) NDB 8.0.18
    Type or units unsigned
    Default [none]
    Range 1 - 144
    Restart Type IS

    A unique node ID is used as the node's address for all cluster internal messages. For data nodes, this is an integer in the range 1 to 144 inclusive. (In NDB 8.0.17 and earlier, this was 1 to 48 inclusive.) Each node in the cluster must have a unique identifier.

    NodeId is the only supported parameter name to use when identifying data nodes.

  • ExecuteOnComputer

    Version (or later) NDB 8.0.13
    Type or units name
    Default [none]
    Range ...
    Restart Type S
    Deprecated Yes (in NDB 7.5)

    This refers to the Id set for one of the computers defined in a [computer] section.

    Important

    This parameter is deprecated, and is subject to removal in a future release. Use the HostName parameter instead.

  • The node ID for this node can be given out only to connections that explicitly request it. A management server that requests any node ID cannot use this one. This parameter can be used when running multiple management servers on the same host, and HostName is not sufficient for distinguishing among processes. Intended for use in testing.

  • HostName

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default localhost
    Range ...
    Restart Type N

    Specifying this parameter defines the hostname of the computer on which the data node is to reside. To specify a hostname other than localhost, either this parameter or ExecuteOnComputer is required.

  • ServerPort

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 64K
    Restart Type S

    Each node in the cluster uses a port to connect to other nodes. By default, this port is allocated dynamically in such a way as to ensure that no two nodes on the same host computer receive the same port number, so it should normally not be necessary to specify a value for this parameter.

    However, if you need to be able to open specific ports in a firewall to permit communication between data nodes and API nodes (including SQL nodes), you can set this parameter to the number of the desired port in an [ndbd] section or (if you need to do this for multiple data nodes) the [ndbd default] section of the config.ini file, and then open the port having that number for incoming connections from SQL nodes, API nodes, or both.

    Note

    Connections from data nodes to management nodes is done using the ndb_mgmd management port (the management server's PortNumber) so outgoing connections to that port from any data nodes should always be permitted.

  • TcpBind_INADDR_ANY

    Setting this parameter to TRUE or 1 binds IP_ADDR_ANY so that connections can be made from anywhere (for autogenerated connections). The default is FALSE (0).

  • NodeGroup

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 0 - 65536
    Restart Type IS

    This parameter can be used to assign a data node to a specific node group. It is read only when the cluster is started for the first time, and cannot be used to reassign a data node to a different node group online. It is generally not desirable to use this parameter in the [ndbd default] section of the config.ini file, and care must be taken not to assign nodes to node groups in such a way that an invalid numbers of nodes are assigned to any node groups.

    The NodeGroup parameter is chiefly intended for use in adding a new node group to a running NDB Cluster without having to perform a rolling restart. For this purpose, you should set it to 65536 (the maximum value). You are not required to set a NodeGroup value for all cluster data nodes, only for those nodes which are to be started and added to the cluster as a new node group at a later time. For more information, see Section 23.5.7.3, “Adding NDB Cluster Data Nodes Online: Detailed Example”.

  • LocationDomainId

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 16
    Restart Type S

    Assigns a data node to a specific availability domain (also known as an availability zone) within a cloud. By informing NDB which nodes are in which availability domains, performance can be improved in a cloud environment in the following ways:

    • If requested data is not found on the same node, reads can be directed to another node in the same availability domain.

    • Communication between nodes in different availability domains are guaranteed to use NDB transporters' WAN support without any further manual intervention.

    • The transporter's group number can be based on which availability domain is used, such that also SQL and other API nodes communicate with local data nodes in the same availability domain whenever possible.

    • The arbitrator can be selected from an availability domain in which no data nodes are present, or, if no such availability domain can be found, from a third availability domain.

    LocationDomainId takes an integer value between 0 and 16 inclusive, with 0 being the default; using 0 is the same as leaving the parameter unset.

  • NoOfReplicas

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 2
    Range 1 - 2
    Restart Type IS
    Version (or later) NDB 8.0.19
    Type or units integer
    Default 2
    Range 1 - 4
    Restart Type IS

    This global parameter can be set only in the [ndbd default] section, and defines the number of fragment replicas for each table stored in the cluster. This parameter also specifies the size of node groups. A node group is a set of nodes all storing the same information.

    Node groups are formed implicitly. The first node group is formed by the set of data nodes with the lowest node IDs, the next node group by the set of the next lowest node identities, and so on. By way of example, assume that we have 4 data nodes and that NoOfReplicas is set to 2. The four data nodes have node IDs 2, 3, 4 and 5. Then the first node group is formed from nodes 2 and 3, and the second node group by nodes 4 and 5. It is important to configure the cluster in such a manner that nodes in the same node groups are not placed on the same computer because a single hardware failure would cause the entire cluster to fail.

    If no node IDs are provided, the order of the data nodes is the determining factor for the node group. Whether or not explicit assignments are made, they can be viewed in the output of the management client's SHOW command.

    The default value for NoOfReplicas is 2. This is the recommended value for most production environments, and prior to NDB 8.0.18, it was the maximum value supported. Beginning with NDB 8.0.19, setting this parameter's value to 3 or 4 is fully tested and supported in production.

    Warning

    Setting NoOfReplicas to 1 means that there is only a single copy of all Cluster data; in this case, the loss of a single data node causes the cluster to fail because there are no additional copies of the data stored by that node.

    The number of data nodes in the cluster must be evenly divisible by the value of this parameter. For example, if there are two data nodes, then NoOfReplicas must be equal to either 1 or 2, since 2/3 and 2/4 both yield fractional values; if there are four data nodes, then NoOfReplicas must be equal to 1, 2, or 4.

  • DataDir

    Version (or later) NDB 8.0.13
    Type or units path
    Default .
    Range ...
    Restart Type IN

    This parameter specifies the directory where trace files, log files, pid files and error logs are placed.

    The default is the data node process working directory.

  • FileSystemPath

    Version (or later) NDB 8.0.13
    Type or units path
    Default DataDir
    Range ...
    Restart Type IN

    This parameter specifies the directory where all files created for metadata, REDO logs, UNDO logs (for Disk Data tables), and data files are placed. The default is the directory specified by DataDir.

    Note

    This directory must exist before the ndbd process is initiated.

    The recommended directory hierarchy for NDB Cluster includes /var/lib/mysql-cluster, under which a directory for the node's file system is created. The name of this subdirectory contains the node ID. For example, if the node ID is 2, this subdirectory is named ndb_2_fs.

  • BackupDataDir

    Version (or later) NDB 8.0.13
    Type or units path
    Default FileSystemPath
    Range ...
    Restart Type IN

    This parameter specifies the directory in which backups are placed.

    Important

    The string '/BACKUP' is always appended to this value. For example, if you set the value of BackupDataDir to /var/lib/cluster-data, then all backups are stored under /var/lib/cluster-data/BACKUP. This also means that the effective default backup location is the directory named BACKUP under the location specified by the FileSystemPath parameter.

Data Memory, Index Memory, and String Memory

DataMemory and IndexMemory are [ndbd] parameters specifying the size of memory segments used to store the actual records and their indexes. In setting values for these, it is important to understand how DataMemory is used, as it usually needs to be updated to reflect actual usage by the cluster.

Note

IndexMemory is deprecated, and subject to removal in a future version of NDB Cluster. See the descriptions that follow for further information.

  • DataMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 98M
    Range 1M - 1T
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units bytes
    Default 98M
    Range 1M - 16T
    Restart Type N

    This parameter defines the amount of space (in bytes) available for storing database records. The entire amount specified by this value is allocated in memory, so it is extremely important that the machine has sufficient physical memory to accommodate it.

    The memory allocated by DataMemory is used to store both the actual records and indexes. There is a 16-byte overhead on each record; an additional amount for each record is incurred because it is stored in a 32KB page with 128 byte page overhead (see below). There is also a small amount wasted per page due to the fact that each record is stored in only one page.

    For variable-size table attributes, the data is stored on separate data pages, allocated from DataMemory. Variable-length records use a fixed-size part with an extra overhead of 4 bytes to reference the variable-size part. The variable-size part has 2 bytes overhead plus 2 bytes per attribute.

    As of NDB 8.0.18, the maximum record size is 30000 bytes. Previously, this was 14000 bytes.

    Resources assigned to DataMemory are used for storing all data and indexes. (Any memory configured as IndexMemory is automatically added to that used by DataMemory to form a common resource pool.)

    Currently, NDB Cluster can use a maximum of 512 MB for hash indexes per partition, which means in some cases it is possible to get Table is full errors in MySQL client applications even when ndb_mgm -e "ALL REPORT MEMORYUSAGE" shows significant free DataMemory. This can also pose a problem with data node restarts on nodes that are heavily loaded with data.

    You can control the number of partitions per local data manager for a given table by setting the NDB_TABLE option PARTITION_BALANCE to one of the values FOR_RA_BY_LDM, FOR_RA_BY_LDM_X_2, FOR_RA_BY_LDM_X_3, or FOR_RA_BY_LDM_X_4, for 1, 2, 3, or 4 partitions per LDM, respectively, when creating the table (see Section 13.1.20.11, “Setting NDB_TABLE Options”).

    Note

    In previous versions of NDB Cluster it was possible to create extra partitions for NDB Cluster tables and thus have more memory available for hash indexes by using the MAX_ROWS option for CREATE TABLE. While still supported for backward compatibility, using MAX_ROWS for this purpose is deprecated; you should use PARTITION_BALANCE instead.

    You can also use the MinFreePct configuration parameter to help avoid problems with node restarts.

    The memory space allocated by DataMemory consists of 32KB pages, which are allocated to table fragments. Each table is normally partitioned into the same number of fragments as there are data nodes in the cluster. Thus, for each node, there are the same number of fragments as are set in NoOfReplicas.

    Once a page has been allocated, it is currently not possible to return it to the pool of free pages, except by deleting the table. (This also means that DataMemory pages, once allocated to a given table, cannot be used by other tables.) Performing a data node recovery also compresses the partition because all records are inserted into empty partitions from other live nodes.

    The DataMemory memory space also contains UNDO information: For each update, a copy of the unaltered record is allocated in the DataMemory. There is also a reference to each copy in the ordered table indexes. Unique hash indexes are updated only when the unique index columns are updated, in which case a new entry in the index table is inserted and the old entry is deleted upon commit. For this reason, it is also necessary to allocate enough memory to handle the largest transactions performed by applications using the cluster. In any case, performing a few large transactions holds no advantage over using many smaller ones, for the following reasons:

    • Large transactions are not any faster than smaller ones

    • Large transactions increase the number of operations that are lost and must be repeated in event of transaction failure

    • Large transactions use more memory

    The default value for DataMemory in NDB 8.0 is 98MB. The minimum value is 1MB. There is no maximum size, but in reality the maximum size has to be adapted so that the process does not start swapping when the limit is reached. This limit is determined by the amount of physical RAM available on the machine and by the amount of memory that the operating system may commit to any one process. 32-bit operating systems are generally limited to 2−4GB per process; 64-bit operating systems can use more. For large databases, it may be preferable to use a 64-bit operating system for this reason.

  • IndexMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 1M - 1T
    Restart Type N
    Deprecated Yes (in NDB 7.6)

    The IndexMemory parameter is deprecated (and subject to future removal); any memory assigned to IndexMemory is allocated instead to the same pool as DataMemory, which is solely responsible for all resources needed for storing data and indexes in memory. In NDB 8.0, the use of IndexMemory in the cluster configuration file triggers a warning from the management server.

    You can estimate the size of a hash index using this formula:

      size  = ( (fragments * 32K) + (rows * 18) )
              * fragment_replicas
    

    fragments is the number of fragments, fragment_replicas is the number of fragment replicas (normally 2), and rows is the number of rows. If a table has one million rows, eight fragments, and two fragment replicas, the expected index memory usage is calculated as shown here:

      ((8 * 32K) + (1000000 * 18)) * 2 = ((8 * 32768) + (1000000 * 18)) * 2
      = (262144 + 18000000) * 2
      = 18262144 * 2 = 36524288 bytes = ~35MB
    

    Index statistics for ordered indexes (when these are enabled) are stored in the mysql.ndb_index_stat_sample table. Since this table has a hash index, this adds to index memory usage. An upper bound to the number of rows for a given ordered index can be calculated as follows:

      sample_size= key_size + ((key_attributes + 1) * 4)
    
      sample_rows = IndexStatSaveSize
                    * ((0.01 * IndexStatSaveScale * log2(rows * sample_size)) + 1)
                    / sample_size
    

    In the preceding formula, key_size is the size of the ordered index key in bytes, key_attributes is the number ot attributes in the ordered index key, and rows is the number of rows in the base table.

    Assume that table t1 has 1 million rows and an ordered index named ix1 on two four-byte integers. Assume in addition that IndexStatSaveSize and IndexStatSaveScale are set to their default values (32K and 100, respectively). Using the previous 2 formulas, we can calculate as follows:

      sample_size = 8  + ((1 + 2) * 4) = 20 bytes
    
      sample_rows = 32K
                    * ((0.01 * 100 * log2(1000000*20)) + 1)
                    / 20
                    = 32768 * ( (1 * ~16.811) +1) / 20
                    = 32768 * ~17.811 / 20
                    = ~29182 rows
    

    The expected index memory usage is thus 2 * 18 * 29182 = ~1050550 bytes.

    In NDB 8.0, the minimum and default vaue for this parameter is 0 (zero).

  • StringMemory

    Version (or later) NDB 8.0.13
    Type or units % or bytes
    Default 25
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type S

    This parameter determines how much memory is allocated for strings such as table names, and is specified in an [ndbd] or [ndbd default] section of the config.ini file. A value between 0 and 100 inclusive is interpreted as a percent of the maximum default value, which is calculated based on a number of factors including the number of tables, maximum table name size, maximum size of .FRM files, MaxNoOfTriggers, maximum column name size, and maximum default column value.

    A value greater than 100 is interpreted as a number of bytes.

    The default value is 25—that is, 25 percent of the default maximum.

    Under most circumstances, the default value should be sufficient, but when you have a great many NDB tables (1000 or more), it is possible to get Error 773 Out of string memory, please modify StringMemory config parameter: Permanent error: Schema error, in which case you should increase this value. 25 (25 percent) is not excessive, and should prevent this error from recurring in all but the most extreme conditions.

The following example illustrates how memory is used for a table. Consider this table definition:

CREATE TABLE example (
  a INT NOT NULL,
  b INT NOT NULL,
  c INT NOT NULL,
  PRIMARY KEY(a),
  UNIQUE(b)
) ENGINE=NDBCLUSTER;

For each record, there are 12 bytes of data plus 12 bytes overhead. Having no nullable columns saves 4 bytes of overhead. In addition, we have two ordered indexes on columns a and b consuming roughly 10 bytes each per record. There is a primary key hash index on the base table using roughly 29 bytes per record. The unique constraint is implemented by a separate table with b as primary key and a as a column. This other table consumes an additional 29 bytes of index memory per record in the example table as well 8 bytes of record data plus 12 bytes of overhead.

Thus, for one million records, we need 58MB for index memory to handle the hash indexes for the primary key and the unique constraint. We also need 64MB for the records of the base table and the unique index table, plus the two ordered index tables.

You can see that hash indexes takes up a fair amount of memory space; however, they provide very fast access to the data in return. They are also used in NDB Cluster to handle uniqueness constraints.

Currently, the only partitioning algorithm is hashing and ordered indexes are local to each node. Thus, ordered indexes cannot be used to handle uniqueness constraints in the general case.

An important point for both IndexMemory and DataMemory is that the total database size is the sum of all data memory and all index memory for each node group. Each node group is used to store replicated information, so if there are four nodes with two fragment replicas, there are two node groups. Thus, the total data memory available is 2 × DataMemory for each data node.

It is highly recommended that DataMemory and IndexMemory be set to the same values for all nodes. Data distribution is even over all nodes in the cluster, so the maximum amount of space available for any node can be no greater than that of the smallest node in the cluster.

DataMemory can be changed, but decreasing it can be risky; doing so can easily lead to a node or even an entire NDB Cluster that is unable to restart due to there being insufficient memory space. Increasing these values should be acceptable, but it is recommended that such upgrades are performed in the same manner as a software upgrade, beginning with an update of the configuration file, and then restarting the management server followed by restarting each data node in turn.

MinFreePct.  A proportion (5% by default) of data node resources including DataMemory is kept in reserve to insure that the data node does not exhaust its memory when performing a restart. This can be adjusted using the MinFreePct data node configuration parameter (default 5).

Version (or later) NDB 8.0.13
Type or units unsigned
Default 5
Range 0 - 100
Restart Type N

Updates do not increase the amount of index memory used. Inserts take effect immediately; however, rows are not actually deleted until the transaction is committed.

Transaction parameters.  The next few [ndbd] parameters that we discuss are important because they affect the number of parallel transactions and the sizes of transactions that can be handled by the system. MaxNoOfConcurrentTransactions sets the number of parallel transactions possible in a node. MaxNoOfConcurrentOperations sets the number of records that can be in update phase or locked simultaneously.

Both of these parameters (especially MaxNoOfConcurrentOperations) are likely targets for users setting specific values and not using the default value. The default value is set for systems using small transactions, to ensure that these do not use excessive memory.

MaxDMLOperationsPerTransaction sets the maximum number of DML operations that can be performed in a given transaction.

  • MaxNoOfConcurrentTransactions

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 4096
    Range 32 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated NDB 8.0.19

    Each cluster data node requires a transaction record for each active transaction in the cluster. The task of coordinating transactions is distributed among all of the data nodes. The total number of transaction records in the cluster is the number of transactions in any given node times the number of nodes in the cluster.

    Transaction records are allocated to individual MySQL servers. Each connection to a MySQL server requires at least one transaction record, plus an additional transaction object per table accessed by that connection. This means that a reasonable minimum for the total number of transactions in the cluster can be expressed as

    TotalNoOfConcurrentTransactions =
        (maximum number of tables accessed in any single transaction + 1)
        * number of SQL nodes
    

    Suppose that there are 10 SQL nodes using the cluster. A single join involving 10 tables requires 11 transaction records; if there are 10 such joins in a transaction, then 10 * 11 = 110 transaction records are required for this transaction, per MySQL server, or 110 * 10 = 1100 transaction records total. Each data node can be expected to handle TotalNoOfConcurrentTransactions / number of data nodes. For an NDB Cluster having 4 data nodes, this would mean setting MaxNoOfConcurrentTransactions on each data node to 1100 / 4 = 275. In addition, you should provide for failure recovery by ensuring that a single node group can accommodate all concurrent transactions; in other words, that each data node's MaxNoOfConcurrentTransactions is sufficient to cover a number of transactions equal to TotalNoOfConcurrentTransactions / number of node groups. If this cluster has a single node group, then MaxNoOfConcurrentTransactions should be set to 1100 (the same as the total number of concurrent transactions for the entire cluster).

    In addition, each transaction involves at least one operation; for this reason, the value set for MaxNoOfConcurrentTransactions should always be no more than the value of MaxNoOfConcurrentOperations.

    This parameter must be set to the same value for all cluster data nodes. This is due to the fact that, when a data node fails, the oldest surviving node re-creates the transaction state of all transactions that were ongoing in the failed node.

    It is possible to change this value using a rolling restart, but the amount of traffic on the cluster must be such that no more transactions occur than the lower of the old and new levels while this is taking place.

    The default value is 4096.

  • MaxNoOfConcurrentOperations

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 32K
    Range 32 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    It is a good idea to adjust the value of this parameter according to the size and number of transactions. When performing transactions which involve only a few operations and records, the default value for this parameter is usually sufficient. Performing large transactions involving many records usually requires that you increase its value.

    Records are kept for each transaction updating cluster data, both in the transaction coordinator and in the nodes where the actual updates are performed. These records contain state information needed to find UNDO records for rollback, lock queues, and other purposes.

    This parameter should be set at a minimum to the number of records to be updated simultaneously in transactions, divided by the number of cluster data nodes. For example, in a cluster which has four data nodes and which is expected to handle one million concurrent updates using transactions, you should set this value to 1000000 / 4 = 250000. To help provide resiliency against failures, it is suggested that you set this parameter to a value that is high enough to permit an individual data node to handle the load for its node group. In other words, you should set the value equal to total number of concurrent operations / number of node groups. (In the case where there is a single node group, this is the same as the total number of concurrent operations for the entire cluster.)

    Because each transaction always involves at least one operation, the value of MaxNoOfConcurrentOperations should always be greater than or equal to the value of MaxNoOfConcurrentTransactions.

    Read queries which set locks also cause operation records to be created. Some extra space is allocated within individual nodes to accommodate cases where the distribution is not perfect over the nodes.

    When queries make use of the unique hash index, there are actually two operation records used per record in the transaction. The first record represents the read in the index table and the second handles the operation on the base table.

    The default value is 32768.

    This parameter actually handles two values that can be configured separately. The first of these specifies how many operation records are to be placed with the transaction coordinator. The second part specifies how many operation records are to be local to the database.

    A very large transaction performed on an eight-node cluster requires as many operation records in the transaction coordinator as there are reads, updates, and deletes involved in the transaction. However, the operation records of the are spread over all eight nodes. Thus, if it is necessary to configure the system for one very large transaction, it is a good idea to configure the two parts separately. MaxNoOfConcurrentOperations is always used to calculate the number of operation records in the transaction coordinator portion of the node.

    It is also important to have an idea of the memory requirements for operation records. These consume about 1KB per record.

  • MaxNoOfLocalOperations

    Version (or later) NDB 8.0.13
    Type or units integer
    Default UNDEFINED
    Range 32 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated NDB 8.0.19

    By default, this parameter is calculated as 1.1 × MaxNoOfConcurrentOperations. This fits systems with many simultaneous transactions, none of them being very large. If there is a need to handle one very large transaction at a time and there are many nodes, it is a good idea to override the default value by explicitly specifying this parameter.

    This parameter is deprecated as of NDB 8.0.19, and is subject to removal in a future NDB Cluster release. In addition, this parameter is incompatible with the TransactionMemory parameter; if you try to set values for both parameters in the cluster configuration file (config.ini), the management server refuses to start.

  • MaxDMLOperationsPerTransaction

    Version (or later) NDB 8.0.13
    Type or units operations (DML)
    Default 4294967295
    Range 32 - 4294967295
    Restart Type N

    This parameter limits the size of a transaction. The transaction is aborted if it requires more than this many DML operations. The minimum number of operations per transaction is 32; however, you can set MaxDMLOperationsPerTransaction to 0 to disable any limitation on the number of DML operations per transaction. The maximum (and default) is 4294967295.

    The value of this parameter cannot exceed that set for MaxNoOfConcurrentOperations.

Transaction temporary storage.  The next set of [ndbd] parameters is used to determine temporary storage when executing a statement that is part of a Cluster transaction. All records are released when the statement is completed and the cluster is waiting for the commit or rollback.

The default values for these parameters are adequate for most situations. However, users with a need to support transactions involving large numbers of rows or operations may need to increase these values to enable better parallelism in the system, whereas users whose applications require relatively small transactions can decrease the values to save memory.

  • MaxNoOfConcurrentIndexOperations

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 8K
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated NDB 8.0.19

    For queries using a unique hash index, another temporary set of operation records is used during a query's execution phase. This parameter sets the size of that pool of records. Thus, this record is allocated only while executing a part of a query. As soon as this part has been executed, the record is released. The state needed to handle aborts and commits is handled by the normal operation records, where the pool size is set by the parameter MaxNoOfConcurrentOperations.

    The default value of this parameter is 8192. Only in rare cases of extremely high parallelism using unique hash indexes should it be necessary to increase this value. Using a smaller value is possible and can save memory if the DBA is certain that a high degree of parallelism is not required for the cluster.

    This parameter is deprecated as of NDB 8.0.19, and is subject to removal in a future NDB Cluster release. In addition, this parameter is incompatible with the TransactionMemory parameter; if you try to set values for both parameters in the cluster configuration file (config.ini), the management server refuses to start.

  • MaxNoOfFiredTriggers

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 4000
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated NDB 8.0.19

    The default value of MaxNoOfFiredTriggers is 4000, which is sufficient for most situations. In some cases it can even be decreased if the DBA feels certain the need for parallelism in the cluster is not high.

    A record is created when an operation is performed that affects a unique hash index. Inserting or deleting a record in a table with unique hash indexes or updating a column that is part of a unique hash index fires an insert or a delete in the index table. The resulting record is used to represent this index table operation while waiting for the original operation that fired it to complete. This operation is short-lived but can still require a large number of records in its pool for situations with many parallel write operations on a base table containing a set of unique hash indexes.

    This parameter is deprecated as of NDB 8.0.19, and is subject to removal in a future NDB Cluster release. In addition, this parameter is incompatible with the TransactionMemory parameter; if you try to set values for both parameters in the cluster configuration file (config.ini), the management server refuses to start.

  • TransactionBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 1M
    Range 1K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    The memory affected by this parameter is used for tracking operations fired when updating index tables and reading unique indexes. This memory is used to store the key and column information for these operations. It is only very rarely that the value for this parameter needs to be altered from the default.

    The default value for TransactionBufferMemory is 1MB.

    Normal read and write operations use a similar buffer, whose usage is even more short-lived. The compile-time parameter ZATTRBUF_FILESIZE (found in ndb/src/kernel/blocks/Dbtc/Dbtc.hpp) set to 4000 × 128 bytes (500KB). A similar buffer for key information, ZDATABUF_FILESIZE (also in Dbtc.hpp) contains 4000 × 16 = 62.5KB of buffer space. Dbtc is the module that handles transaction coordination.

Transaction resource allocation parameters.  The parameters in the following list are used to allocate transaction resources in the transaction coordinator (DBTC). Leaving any one of these set to the default (0) dedicates transaction memory for 25% of estimated total data node usage for the corresponding resource. The actual maximum possible values for these parameters are typically limited by the amount of memory available to the data node; setting them has no impact on the total amount of memory allocated to the data node. In addition, you should keep in mind that they control numbers of reserved internal records for the data node independent of any settings for MaxDMLOperationsPerTransaction, MaxNoOfConcurrentIndexOperations, MaxNoOfConcurrentOperations, MaxNoOfConcurrentScans, MaxNoOfConcurrentTransactions, MaxNoOfFiredTriggers, MaxNoOfLocalScans, or TransactionBufferMemory (see Transaction parameters and Transaction temporary storage).

  • ReservedConcurrentIndexOperations

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of simultaneous index operations having dedicated resources on one data node.

  • ReservedConcurrentOperations

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of simultaneous operations having dedicated resources in transaction coordinators on one data node.

  • ReservedConcurrentScans

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of simultaneous scans having dedicated resources on one data node.

  • ReservedConcurrentTransactions

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of simultaneous transactions having dedicated resources on one data node.

  • ReservedFiredTriggers

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of triggers that have dedicated resources on one ndbd(DB) node.

  • ReservedLocalScans

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16

    Number of simultaneous fragment scans having dedicated resources on one data node.

  • ReservedTransactionBufferMemory

    Version (or later) NDB 8.0.16
    Type or units numeric
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Added NDB 8.0.16
    Deprecated NDB 8.0.19

    Dynamic buffer space (in bytes) for key and attribute data allocated to each data node.

  • TransactionMemory

    Version (or later) NDB 8.0.19
    Type or units bytes
    Default 0
    Range 0 - 16384G
    Restart Type N
    Added NDB 8.0.19

    This parameter determines the memory (in bytes) allocated for transactions on each data node. Setting of transaction memory can be handled in any one of the three ways listed here:

    • A number of configuration parameters are incompatible with TransactionMemory. If any of these are set, transaction memory is calculated as it was previous to NDB 8.0.19. You should be aware that it is not possible to set any of these parameters concurrently with TransactionMemory; if you attempt to do so, the management server is unable to start (see Parameters incompatible with TransactionMemory).

    • If TransactionMemory is set, this value is used for determining transaction memory.

    • If neither any incompatible parameters are set nor TransactionMemory is set, transaction memory is set by NDB to 10% of the value of the DataMemory configuration parameter.

    Parameters incompatible with TransactionMemory.  The following parameters cannot be used concurrently with TransactionMemory and are deprecated as of NDB 8.0.19:

    Explicitly setting any of the parameters just listed when TransactionMemory has also been set in the cluster configuration file (config.ini) keeps the management node from starting.

    For more information regarding resource allocation in NDB Cluster data nodes, see Section 23.3.3.13, “Data Node Memory Management”.

Scans and buffering.  There are additional [ndbd] parameters in the Dblqh module (in ndb/src/kernel/blocks/Dblqh/Dblqh.hpp) that affect reads and updates. These include ZATTRINBUF_FILESIZE, set by default to 10000 × 128 bytes (1250KB) and ZDATABUF_FILE_SIZE, set by default to 10000*16 bytes (roughly 156KB) of buffer space. To date, there have been neither any reports from users nor any results from our own extensive tests suggesting that either of these compile-time limits should be increased.

  • BatchSizePerLocalScan

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 256
    Range 1 - 992
    Restart Type N
    Deprecated NDB 8.0.19

    This parameter is used to calculate the number of lock records used to handle concurrent scan operations.

    BatchSizePerLocalScan has a strong connection to the BatchSize defined in the SQL nodes.

    Deprecated as of NDB 8.0.19.

  • LongMessageBuffer

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 64M
    Range 512K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This is an internal buffer used for passing messages within individual nodes and between nodes. The default is 64MB.

    This parameter seldom needs to be changed from the default.

  • MaxFKBuildBatchSize

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 64
    Range 16 - 512
    Restart Type S

    Maximum scan batch size used for building foreign keys. Increasing the value set for this parameter may speed up building of foreign key builds at the expense of greater impact to ongoing traffic.

  • MaxNoOfConcurrentScans

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 256
    Range 2 - 500
    Restart Type N

    This parameter is used to control the number of parallel scans that can be performed in the cluster. Each transaction coordinator can handle the number of parallel scans defined for this parameter. Each scan query is performed by scanning all partitions in parallel. Each partition scan uses a scan record in the node where the partition is located, the number of records being the value of this parameter times the number of nodes. The cluster should be able to sustain MaxNoOfConcurrentScans scans concurrently from all nodes in the cluster.

    Scans are actually performed in two cases. The first of these cases occurs when no hash or ordered indexes exists to handle the query, in which case the query is executed by performing a full table scan. The second case is encountered when there is no hash index to support the query but there is an ordered index. Using the ordered index means executing a parallel range scan. The order is kept on the local partitions only, so it is necessary to perform the index scan on all partitions.

    The default value of MaxNoOfConcurrentScans is 256. The maximum value is 500.

  • MaxNoOfLocalScans

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 4 * MaxNoOfConcurrentScans * [# of data nodes] + 2
    Range 32 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated NDB 8.0.19

    Specifies the number of local scan records if many scans are not fully parallelized. When the number of local scan records is not provided, it is calculated as shown here:

    4 * MaxNoOfConcurrentScans * [# data nodes] + 2
    

    This parameter is deprecated as of NDB 8.0.19, and is subject to removal in a future NDB Cluster release. In addition, this parameter is incompatible with the TransactionMemory parameter; if you try to set values for both parameters in the cluster configuration file (config.ini), the management server refuses to start.

  • MaxParallelCopyInstances

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 64
    Restart Type S

    This parameter sets the parallelization used in the copy phase of a node restart or system restart, when a node that is currently just starting is synchronised with a node that already has current data by copying over any changed records from the node that is up to date. Because full parallelism in such cases can lead to overload situations, MaxParallelCopyInstances provides a means to decrease it. This parameter's default value 0. This value means that the effective parallelism is equal to the number of LDM instances in the node just starting as well as the node updating it.

  • MaxParallelScansPerFragment

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 256
    Range 1 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    It is possible to configure the maximum number of parallel scans (TUP scans and TUX scans) allowed before they begin queuing for serial handling. You can increase this to take advantage of any unused CPU when performing large number of scans in parallel and improve their performance.

  • MaxReorgBuildBatchSize

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 64
    Range 16 - 512
    Restart Type S

    Maximum scan batch size used for reorganization of table partitions. Increasing the value set for this parameter may speed up reorganization at the expense of greater impact to ongoing traffic.

  • MaxUIBuildBatchSize

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 64
    Range 16 - 512
    Restart Type S

    Maximum scan batch size used for building unique keys. Increasing the value set for this parameter may speed up such builds at the expense of greater impact to ongoing traffic.

Memory Allocation

MaxAllocate

Version (or later) NDB 8.0.13
Type or units unsigned
Default 32M
Range 1M - 1G
Restart Type N

This is the maximum size of the memory unit to use when allocating memory for tables. In cases where NDB gives Out of memory errors, but it is evident by examining the cluster logs or the output of DUMP 1000 that all available memory has not yet been used, you can increase the value of this parameter (or MaxNoOfTables, or both) to cause NDB to make sufficient memory available.

Multiple Transporters

Beginning with version 8.0.20, NDB allocates multiple transporters for communication between pairs of data nodes. The number of transporters so allocated can be influenced by setting an appropriate value for the NodeGroupTransporters parameter introduced in that release.

NodeGroupTransporters

Version (or later) NDB 8.0.20
Type or units integer
Default 0
Range 0 - 32
Restart Type N
Added NDB 8.0.20

This parameter determines the number of transporters used between nodes in the same node group. The default value (0) means that the number of transporters used is the same as the number of LDMs in the node. This should be sufficient for most use cases; thus it should seldom be necessary to change this value from its default.

Setting NodeGroupTransporters to a number greater than the number of LDM threads or the number of TC threads, whichever is higher, causes NDB to use the maximum of these two numbers of threads. This means that a value greater than this is effectively ignored.

Hash Map Size

DefaultHashMapSize

Version (or later) NDB 8.0.13
Type or units LDM threads
Default 240
Range 0 - 3840
Restart Type N

The original intended use for this parameter was to facilitate upgrades and especially downgrades to and from very old releases with differing default hash map sizes. This is not an issue when upgrading from NDB Cluster 7.3 (or later) to later versions.

Decreasing this parameter online after any tables have been created or modified with DefaultHashMapSize equal to 3840 is not currently supported.

Logging and checkpointing.  The following [ndbd] parameters control log and checkpoint behavior.

  • FragmentLogFileSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 16M
    Range 4M - 1G
    Restart Type IN

    Setting this parameter enables you to control directly the size of redo log files. This can be useful in situations when NDB Cluster is operating under a high load and it is unable to close fragment log files quickly enough before attempting to open new ones (only 2 fragment log files can be open at one time); increasing the size of the fragment log files gives the cluster more time before having to open each new fragment log file. The default value for this parameter is 16M.

    For more information about fragment log files, see the description for NoOfFragmentLogFiles.

  • InitialNoOfOpenFiles

    Version (or later) NDB 8.0.13
    Type or units files
    Default 27
    Range 20 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets the initial number of internal threads to allocate for open files.

    The default value is 27.

  • InitFragmentLogFiles

    Version (or later) NDB 8.0.13
    Type or units [see values]
    Default SPARSE
    Range SPARSE, FULL
    Restart Type IN

    By default, fragment log files are created sparsely when performing an initial start of a data node—that is, depending on the operating system and file system in use, not all bytes are necessarily written to disk. However, it is possible to override this behavior and force all bytes to be written, regardless of the platform and file system type being used, by means of this parameter. InitFragmentLogFiles takes either of two values:

    • SPARSE. Fragment log files are created sparsely. This is the default value.

    • FULL. Force all bytes of the fragment log file to be written to disk.

    Depending on your operating system and file system, setting InitFragmentLogFiles=FULL may help eliminate I/O errors on writes to the REDO log.

  • EnablePartialLcp

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default true
    Range ...
    Restart Type N

    When true, enable partial local checkpoints: This means that each LCP records only part of the full database, plus any records containing rows changed since the last LCP; if no rows have changed, the LCP updates only the LCP control file and does not update any data files.

    If EnablePartialLcp is disabled (false), each LCP uses only a single file and writes a full checkpoint; this requires the least amount of disk space for LCPs, but increases the write load for each LCP. The default value is enabled (true). The proportion of space used by partial LCPS can be modified by the setting for the RecoveryWork configuration parameter.

    For more information about files and directories used for full and partial LCPs, see NDB Cluster Data Node File System Directory.

    Setting this parameter to false also disables the calculation of disk write speed used by the adaptive LCP control mechanism.

  • LcpScanProgressTimeout

    Version (or later) NDB 8.0.13
    Type or units second
    Default 60
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units second
    Default 180
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    A local checkpoint fragment scan watchdog checks periodically for no progress in each fragment scan performed as part of a local checkpoint, and shuts down the node if there is no progress after a given amount of time has elapsed. This interval can be set using the LcpScanProgressTimeout data node configuration parameter, which sets the maximum time for which the local checkpoint can be stalled before the LCP fragment scan watchdog shuts down the node.

    The default value is 60 seconds (providing compatibility with previous releases). Setting this parameter to 0 disables the LCP fragment scan watchdog altogether.

  • MaxNoOfOpenFiles

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 20 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets a ceiling on how many internal threads to allocate for open files. Any situation requiring a change in this parameter should be reported as a bug.

    The default value is 0. However, the minimum value to which this parameter can be set is 20.

  • MaxNoOfSavedMessages

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 25
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets the maximum number of errors written in the error log as well as the maximum number of trace files that are kept before overwriting the existing ones. Trace files are generated when, for whatever reason, the node crashes.

    The default is 25, which sets these maximums to 25 error messages and 25 trace files.

  • MaxLCPStartDelay

    Version (or later) NDB 8.0.13
    Type or units seconds
    Default 0
    Range 0 - 600
    Restart Type N

    In parallel data node recovery, only table data is actually copied and synchronized in parallel; synchronization of metadata such as dictionary and checkpoint information is done in a serial fashion. In addition, recovery of dictionary and checkpoint information cannot be executed in parallel with performing of local checkpoints. This means that, when starting or restarting many data nodes concurrently, data nodes may be forced to wait while a local checkpoint is performed, which can result in longer node recovery times.

    It is possible to force a delay in the local checkpoint to permit more (and possibly all) data nodes to complete metadata synchronization; once each data node's metadata synchronization is complete, all of the data nodes can recover table data in parallel, even while the local checkpoint is being executed. To force such a delay, set MaxLCPStartDelay, which determines the number of seconds the cluster can wait to begin a local checkpoint while data nodes continue to synchronize metadata. This parameter should be set in the [ndbd default] section of the config.ini file, so that it is the same for all data nodes. The maximum value is 600; the default is 0.

  • NoOfFragmentLogFiles

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 16
    Range 3 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    This parameter sets the number of REDO log files for the node, and thus the amount of space allocated to REDO logging. Because the REDO log files are organized in a ring, it is extremely important that the first and last log files in the set (sometimes referred to as the head and tail log files, respectively) do not meet. When these approach one another too closely, the node begins aborting all transactions encompassing updates due to a lack of room for new log records.

    A REDO log record is not removed until both required local checkpoints have been completed since that log record was inserted. Checkpointing frequency is determined by its own set of configuration parameters discussed elsewhere in this chapter.

    The default parameter value is 16, which by default means 16 sets of 4 16MB files for a total of 1024MB. The size of the individual log files is configurable using the FragmentLogFileSize parameter. In scenarios requiring a great many updates, the value for NoOfFragmentLogFiles may need to be set as high as 300 or even higher to provide sufficient space for REDO logs.

    If the checkpointing is slow and there are so many writes to the database that the log files are full and the log tail cannot be cut without jeopardizing recovery, all updating transactions are aborted with internal error code 410 (Out of log file space temporarily). This condition prevails until a checkpoint has completed and the log tail can be moved forward.

    Important

    This parameter cannot be changed on the fly; you must restart the node using --initial. If you wish to change this value for all data nodes in a running cluster, you can do so using a rolling node restart (using --initial when starting each data node).

  • RecoveryWork

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 60
    Range 25 - 100
    Restart Type N

    Percentage of storage overhead for LCP files. This parameter has an effect only when EnablePartialLcp is true, that is, only when partial local checkpoints are enabled. A higher value means:

    • Fewer records are written for each LCP, LCPs use more space

    • More work is needed during restarts

    A lower value for RecoveryWork means:

    • More records are written during each LCP, but LCPs require less space on disk.

    • Less work during restart and thus faster restarts, at the expense of more work during normal operations

    For example, setting RecoveryWork to 60 means that the total size of an LCP is roughly 1 + 0.6 = 1.6 times the size of the data to be checkpointed. This means that 60% more work is required during the restore phase of a restart compared to the work done during a restart that uses full checkpoints. (This is more than compensated for during other phases of the restart such that the restart as a whole is still faster when using partial LCPs than when using full LCPs.) In order not to fill up the redo log, it is necessary to write at 1 + (1 / RecoveryWork) times the rate of data changes during checkpoints—thus, when RecoveryWork = 60, it is necessary to write at approximately 1 + (1 / 0.6 ) = 2.67 times the change rate. In other words, if changes are being written at 10 MByte per second, the checkpoint needs to be written at roughly 26.7 MByte per second.

    Setting RecoveryWork = 40 means that only 1.4 times the total LCP size is needed (and thus the restore phase takes 10 to 15 percent less time. In this case, the checkpoint write rate is 3.5 times the rate of change.

    The NDB source distribution includes a test program for simulating LCPs. lcp_simulator.cc can be found in storage/ndb/src/kernel/blocks/backup/. To compile and run it on Unix platforms, execute the commands shown here:

    shell> gcc lcp_simulator.cc
    shell> ./a.out
    

    This program has no dependencies other than stdio.h, and does not require a connection to an NDB cluster or a MySQL server. By default, it simulates 300 LCPs (three sets of 100 LCPs, each consisting of inserts, updates, and deletes, in turn), reporting the size of the LCP after each one. You can alter the simulation by changing the values of recovery_work, insert_work, and delete_work in the source and recompiling. For more information, see the source of the program.

  • InsertRecoveryWork

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 40
    Range 0 - 70
    Restart Type N

    Percentage of RecoveryWork used for inserted rows. A higher value increases the number of writes during a local checkpoint, and decreases the total size of the LCP. A lower value decreases the number of writes during an LCP, but results in more space being used for the LCP, which means that recovery takes longer. This parameter has an effect only when EnablePartialLcp is true, that is, only when partial local checkpoints are enabled.

  • EnableRedoControl

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range ...
    Restart Type N

    Enable adaptive checkpointing speed for controlling redo log usage. Set to false to disable (the default). Setting EnablePartialLcp to false also disables the adaptive calculation.

    When enabled, EnableRedoControl allows the data nodes greater flexibility with regard to the rate at which they write LCPs to disk. More specifically, enabling this parameter means that higher write rates can be employed, so that LCPs can complete and Redo logs be trimmed more quickly, thereby reducing recovery time and disk space requirements. This functionality allows data nodes to make better use of the higher rate of I/O and greater bandwidth available from modern solid-state storage devices and protocols, such as solid-state drives (SSDs) using Non-Volatile Memory Express (NVMe).

    The parameter currently defaults to false (disabled) due to the fact that NDB is still deployed widely on systems whose I/O or bandwidth is constrained relative to those employing solid-state technology, such as those using conventional hard disks (HDDs). In settings such as these, the EnableRedoControl mechanism can easily cause the I/O subsystem to become saturated, increasing wait times for data node input and output. In particular, this can cause issues with NDB Disk Data tables which have tablespaces or log file groups sharing a constrained IO subsystem with data node LCP and redo log files; such problems potentially include node or cluster failure due to GCP stop errors.

Metadata objects.  The next set of [ndbd] parameters defines pool sizes for metadata objects, used to define the maximum number of attributes, tables, indexes, and trigger objects used by indexes, events, and replication between clusters.

Note

These act merely as suggestions to the cluster, and any that are not specified revert to the default values shown.

  • MaxNoOfAttributes

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 1000
    Range 32 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets a suggested maximum number of attributes that can be defined in the cluster; like MaxNoOfTables, it is not intended to function as a hard upper limit.

    (In older NDB Cluster releases, this parameter was sometimes treated as a hard limit for certain operations. This caused problems with NDB Cluster Replication, when it was possible to create more tables than could be replicated, and sometimes led to confusion when it was possible [or not possible, depending on the circumstances] to create more than MaxNoOfAttributes attributes.)

    The default value is 1000, with the minimum possible value being 32. The maximum is 4294967039. Each attribute consumes around 200 bytes of storage per node due to the fact that all metadata is fully replicated on the servers.

    When setting MaxNoOfAttributes, it is important to prepare in advance for any ALTER TABLE statements that you might want to perform in the future. This is due to the fact, during the execution of ALTER TABLE on a Cluster table, 3 times the number of attributes as in the original table are used, and a good practice is to permit double this amount. For example, if the NDB Cluster table having the greatest number of attributes (greatest_number_of_attributes) has 100 attributes, a good starting point for the value of MaxNoOfAttributes would be 6 * greatest_number_of_attributes = 600.

    You should also estimate the average number of attributes per table and multiply this by MaxNoOfTables. If this value is larger than the value obtained in the previous paragraph, you should use the larger value instead.

    Assuming that you can create all desired tables without any problems, you should also verify that this number is sufficient by trying an actual ALTER TABLE after configuring the parameter. If this is not successful, increase MaxNoOfAttributes by another multiple of MaxNoOfTables and test it again.

  • MaxNoOfTables

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 128
    Range 8 - 20320
    Restart Type N

    A table object is allocated for each table and for each unique hash index in the cluster. This parameter sets a suggested maximum number of table objects for the cluster as a whole; like MaxNoOfAttributes, it is not intended to function as a hard upper limit.

    (In older NDB Cluster releases, this parameter was sometimes treated as a hard limit for certain operations. This caused problems with NDB Cluster Replication, when it was possible to create more tables than could be replicated, and sometimes led to confusion when it was possible [or not possible, depending on the circumstances] to create more than MaxNoOfTables tables.)

    For each attribute that has a BLOB data type an extra table is used to store most of the BLOB data. These tables also must be taken into account when defining the total number of tables.

    The default value of this parameter is 128. The minimum is 8 and the maximum is 20320. Each table object consumes approximately 20KB per node.

    Note

    The sum of MaxNoOfTables, MaxNoOfOrderedIndexes, and MaxNoOfUniqueHashIndexes must not exceed 232 − 2 (4294967294).

  • MaxNoOfOrderedIndexes

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 128
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    For each ordered index in the cluster, an object is allocated describing what is being indexed and its storage segments. By default, each index so defined also defines an ordered index. Each unique index and primary key has both an ordered index and a hash index. MaxNoOfOrderedIndexes sets the total number of ordered indexes that can be in use in the system at any one time.

    The default value of this parameter is 128. Each index object consumes approximately 10KB of data per node.

    Note

    The sum of MaxNoOfTables, MaxNoOfOrderedIndexes, and MaxNoOfUniqueHashIndexes must not exceed 232 − 2 (4294967294).

  • MaxNoOfUniqueHashIndexes

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 64
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    For each unique index that is not a primary key, a special table is allocated that maps the unique key to the primary key of the indexed table. By default, an ordered index is also defined for each unique index. To prevent this, you must specify the USING HASH option when defining the unique index.

    The default value is 64. Each index consumes approximately 15KB per node.

    Note

    The sum of MaxNoOfTables, MaxNoOfOrderedIndexes, and MaxNoOfUniqueHashIndexes must not exceed 232 − 2 (4294967294).

  • MaxNoOfTriggers

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 768
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Internal update, insert, and delete triggers are allocated for each unique hash index. (This means that three triggers are created for each unique hash index.) However, an ordered index requires only a single trigger object. Backups also use three trigger objects for each normal table in the cluster.

    Replication between clusters also makes use of internal triggers.

    This parameter sets the maximum number of trigger objects in the cluster.

    The default value is 768.

  • MaxNoOfSubscriptions

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Each NDB table in an NDB Cluster requires a subscription in the NDB kernel. For some NDB API applications, it may be necessary or desirable to change this parameter. However, for normal usage with MySQL servers acting as SQL nodes, there is not any need to do so.

    The default value for MaxNoOfSubscriptions is 0, which is treated as equal to MaxNoOfTables. Each subscription consumes 108 bytes.

  • MaxNoOfSubscribers

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter is of interest only when using NDB Cluster Replication. The default value is 0, which is treated as 2 * MaxNoOfTables; that is, there is one subscription per NDB table for each of two MySQL servers (one acting as the replication source and the other as the replica). Each subscriber uses 16 bytes of memory.

    When using circular replication, multi-source replication, and other replication setups involving more than 2 MySQL servers, you should increase this parameter to the number of mysqld processes included in replication (this is often, but not always, the same as the number of clusters). For example, if you have a circular replication setup using three NDB Clusters, with one mysqld attached to each cluster, and each of these mysqld processes acts as a source and as a replica, you should set MaxNoOfSubscribers equal to 3 * MaxNoOfTables.

    For more information, see Section 23.6, “NDB Cluster Replication”.

  • MaxNoOfConcurrentSubOperations

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 256
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets a ceiling on the number of operations that can be performed by all API nodes in the cluster at one time. The default value (256) is sufficient for normal operations, and might need to be adjusted only in scenarios where there are a great many API nodes each performing a high volume of operations concurrently.

Boolean parameters.  The behavior of data nodes is also affected by a set of [ndbd] parameters taking on boolean values. These parameters can each be specified as TRUE by setting them equal to 1 or Y, and as FALSE by setting them equal to 0 or N.

  • CompressedLCP

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Setting this parameter to 1 causes local checkpoint files to be compressed. The compression used is equivalent to gzip --fast, and can save 50% or more of the space required on the data node to store uncompressed checkpoint files. Compressed LCPs can be enabled for individual data nodes, or for all data nodes (by setting this parameter in the [ndbd default] section of the config.ini file).

    Important

    You cannot restore a compressed local checkpoint to a cluster running a MySQL version that does not support this feature.

    The default value is 0 (disabled).

  • CrashOnCorruptedTuple

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default true
    Range true, false
    Restart Type S

    When this parameter is enabled (the default), it forces a data node to shut down whenever it encounters a corrupted tuple.

  • Diskless

    Version (or later) NDB 8.0.13
    Type or units true|false (1|0)
    Default false
    Range true, false
    Restart Type IS

    It is possible to specify NDB Cluster tables as diskless, meaning that tables are not checkpointed to disk and that no logging occurs. Such tables exist only in main memory. A consequence of using diskless tables is that neither the tables nor the records in those tables survive a crash. However, when operating in diskless mode, it is possible to run ndbd on a diskless computer.

    Important

    This feature causes the entire cluster to operate in diskless mode.

    When this feature is enabled, Cluster online backup is disabled. In addition, a partial start of the cluster is not possible.

    Diskless is disabled by default.

  • LateAlloc

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 1
    Range 0 - 1
    Restart Type N

    Allocate memory for this data node after a connection to the management server has been established. Enabled by default.

  • LockPagesInMainMemory

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 0
    Range 0 - 2
    Restart Type N

    For a number of operating systems, including Solaris and Linux, it is possible to lock a process into memory and so avoid any swapping to disk. This can be used to help guarantee the cluster's real-time characteristics.

    This parameter takes one of the integer values 0, 1, or 2, which act as shown in the following list:

    • 0: Disables locking. This is the default value.

    • 1: Performs the lock after allocating memory for the process.

    • 2: Performs the lock before memory for the process is allocated.

    If the operating system is not configured to permit unprivileged users to lock pages, then the data node process making use of this parameter may have to be run as system root. (LockPagesInMainMemory uses the mlockall function. From Linux kernel 2.6.9, unprivileged users can lock memory as limited by max locked memory. For more information, see ulimit -l and http://linux.die.net/man/2/mlock).

    Note

    In older NDB Cluster releases, this parameter was a Boolean. 0 or false was the default setting, and disabled locking. 1 or true enabled locking of the process after its memory was allocated. NDB Cluster 8.0 treats true or false for the value of this parameter as an error.

    Important

    Beginning with glibc 2.10, glibc uses per-thread arenas to reduce lock contention on a shared pool, which consumes real memory. In general, a data node process does not need per-thread arenas, since it does not perform any memory allocation after startup. (This difference in allocators does not appear to affect performance significantly.)

    The glibc behavior is intended to be configurable via the MALLOC_ARENA_MAX environment variable, but a bug in this mechanism prior to glibc 2.16 meant that this variable could not be set to less than 8, so that the wasted memory could not be reclaimed. (Bug #15907219; see also http://sourceware.org/bugzilla/show_bug.cgi?id=13137 for more information concerning this issue.)

    One possible workaround for this problem is to use the LD_PRELOAD environment variable to preload a jemalloc memory allocation library to take the place of that supplied with glibc.

  • ODirect

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Enabling this parameter causes NDB to attempt using O_DIRECT writes for LCP, backups, and redo logs, often lowering kswapd and CPU usage. When using NDB Cluster on Linux, enable ODirect if you are using a 2.6 or later kernel.

    ODirect is disabled by default.

  • ODirectSyncFlag

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    When this parameter is enabled, redo log writes are performed such that each completed file system write is handled as a call to fsync. The setting for this parameter is ignored if at least one of the following conditions is true:

    • ODirect is not enabled.

    • InitFragmentLogFiles is set to SPARSE.

    Disabled by default.

  • RestartOnErrorInsert

    Version (or later) NDB 8.0.13
    Type or units error code
    Default 2
    Range 0 - 4
    Restart Type N

    This feature is accessible only when building the debug version where it is possible to insert errors in the execution of individual blocks of code as part of testing.

    This feature is disabled by default.

  • StopOnError

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default 1
    Range 0, 1
    Restart Type N

    This parameter specifies whether a data node process should exit or perform an automatic restart when an error condition is encountered.

    This parameter's default value is 1; this means that, by default, an error causes the data node process to halt.

    When an error is encountered and StopOnError is 0, the data node process is restarted.

    Users of MySQL Cluster Manager should note that, when StopOnError equals 1, this prevents the MySQL Cluster Manager agent from restarting any data nodes after it has performed its own restart and recovery. See Starting and Stopping the Agent on Linux, for more information.

  • UseShm

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type S

    Enable a shared memory connection between this data node and the API node also running on this host. Set to 1 to enable.

Controlling Timeouts, Intervals, and Disk Paging

There are a number of [ndbd] parameters specifying timeouts and intervals between various actions in Cluster data nodes. Most of the timeout values are specified in milliseconds. Any exceptions to this are mentioned where applicable.

  • TimeBetweenWatchDogCheck

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 6000
    Range 70 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    To prevent the main thread from getting stuck in an endless loop at some point, a watchdog thread checks the main thread. This parameter specifies the number of milliseconds between checks. If the process remains in the same state after three checks, the watchdog thread terminates it.

    This parameter can easily be changed for purposes of experimentation or to adapt to local conditions. It can be specified on a per-node basis although there seems to be little reason for doing so.

    The default timeout is 6000 milliseconds (6 seconds).

  • TimeBetweenWatchDogCheckInitial

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 6000
    Range 70 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This is similar to the TimeBetweenWatchDogCheck parameter, except that TimeBetweenWatchDogCheckInitial controls the amount of time that passes between execution checks inside a storage node in the early start phases during which memory is allocated.

    The default timeout is 6000 milliseconds (6 seconds).

  • StartPartialTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 30000
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter specifies how long the Cluster waits for all data nodes to come up before the cluster initialization routine is invoked. This timeout is used to avoid a partial Cluster startup whenever possible.

    This parameter is overridden when performing an initial start or initial restart of the cluster.

    The default value is 30000 milliseconds (30 seconds). 0 disables the timeout, in which case the cluster may start only if all nodes are available.

  • StartPartitionedTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    If the cluster is ready to start after waiting for StartPartialTimeout milliseconds but is still possibly in a partitioned state, the cluster waits until this timeout has also passed. If StartPartitionedTimeout is set to 0, the cluster waits indefinitely (232−1 ms, or approximately 49.71 days).

    This parameter is overridden when performing an initial start or initial restart of the cluster.

  • StartFailureTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    If a data node has not completed its startup sequence within the time specified by this parameter, the node startup fails. Setting this parameter to 0 (the default value) means that no data node timeout is applied.

    For nonzero values, this parameter is measured in milliseconds. For data nodes containing extremely large amounts of data, this parameter should be increased. For example, in the case of a data node containing several gigabytes of data, a period as long as 10−15 minutes (that is, 600000 to 1000000 milliseconds) might be required to perform a node restart.

  • StartNoNodeGroupTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 15000
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When a data node is configured with Nodegroup = 65536, is regarded as not being assigned to any node group. When that is done, the cluster waits StartNoNodegroupTimeout milliseconds, then treats such nodes as though they had been added to the list passed to the --nowait-nodes option, and starts. The default value is 15000 (that is, the management server waits 15 seconds). Setting this parameter equal to 0 means that the cluster waits indefinitely.

    StartNoNodegroupTimeout must be the same for all data nodes in the cluster; for this reason, you should always set it in the [ndbd default] section of the config.ini file, rather than for individual data nodes.

    See Section 23.5.7, “Adding NDB Cluster Data Nodes Online”, for more information.

  • HeartbeatIntervalDbDb

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 5000
    Range 10 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    One of the primary methods of discovering failed nodes is by the use of heartbeats. This parameter states how often heartbeat signals are sent and how often to expect to receive them. Heartbeats cannot be disabled.

    After missing four heartbeat intervals in a row, the node is declared dead. Thus, the maximum time for discovering a failure through the heartbeat mechanism is five times the heartbeat interval.

    The default heartbeat interval is 5000 milliseconds (5 seconds). This parameter must not be changed drastically and should not vary widely between nodes. If one node uses 5000 milliseconds and the node watching it uses 1000 milliseconds, obviously the node is declared dead very quickly. This parameter can be changed during an online software upgrade, but only in small increments.

    See also Network communication and latency, as well as the description of the ConnectCheckIntervalDelay configuration parameter.

  • HeartbeatIntervalDbApi

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 1500
    Range 100 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Each data node sends heartbeat signals to each MySQL server (SQL node) to ensure that it remains in contact. If a MySQL server fails to send a heartbeat in time it is declared dead, in which case all ongoing transactions are completed and all resources released. The SQL node cannot reconnect until all activities initiated by the previous MySQL instance have been completed. The three-heartbeat criteria for this determination are the same as described for HeartbeatIntervalDbDb.

    The default interval is 1500 milliseconds (1.5 seconds). This interval can vary between individual data nodes because each data node watches the MySQL servers connected to it, independently of all other data nodes.

    For more information, see Network communication and latency.

  • HeartbeatOrder

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 0
    Range 0 - 65535
    Restart Type S

    Data nodes send heartbeats to one another in a circular fashion whereby each data node monitors the previous one. If a heartbeat is not detected by a given data node, this node declares the previous data node in the circle dead (that is, no longer accessible by the cluster). The determination that a data node is dead is done globally; in other words; once a data node is declared dead, it is regarded as such by all nodes in the cluster.

    It is possible for heartbeats between data nodes residing on different hosts to be too slow compared to heartbeats between other pairs of nodes (for example, due to a very low heartbeat interval or temporary connection problem), such that a data node is declared dead, even though the node can still function as part of the cluster. .

    In this type of situation, it may be that the order in which heartbeats are transmitted between data nodes makes a difference as to whether or not a particular data node is declared dead. If this declaration occurs unnecessarily, this can in turn lead to the unnecessary loss of a node group and as thus to a failure of the cluster.

    Consider a setup where there are 4 data nodes A, B, C, and D running on 2 host computers host1 and host2, and that these data nodes make up 2 node groups, as shown in the following table:

    Table 23.10 Four data nodes A, B, C, D running on two host computers host1, host2; each data node belongs to one of two node groups.

    Node Group Nodes Running on host1 Nodes Running on host2
    Node Group 0: Node A Node B
    Node Group 1: Node C Node D

    Suppose the heartbeats are transmitted in the order A->B->C->D->A. In this case, the loss of the heartbeat between the hosts causes node B to declare node A dead and node C to declare node B dead. This results in loss of Node Group 0, and so the cluster fails. On the other hand, if the order of transmission is A->B->D->C->A (and all other conditions remain as previously stated), the loss of the heartbeat causes nodes A and D to be declared dead; in this case, each node group has one surviving node, and the cluster survives.

    The HeartbeatOrder configuration parameter makes the order of heartbeat transmission user-configurable. The default value for HeartbeatOrder is zero; allowing the default value to be used on all data nodes causes the order of heartbeat transmission to be determined by NDB. If this parameter is used, it must be set to a nonzero value (maximum 65535) for every data node in the cluster, and this value must be unique for each data node; this causes the heartbeat transmission to proceed from data node to data node in the order of their HeartbeatOrder values from lowest to highest (and then directly from the data node having the highest HeartbeatOrder to the data node having the lowest value, to complete the circle). The values need not be consecutive. For example, to force the heartbeat transmission order A->B->D->C->A in the scenario outlined previously, you could set the HeartbeatOrder values as shown here:

    Table 23.11 HeartbeatOrder values to force a heartbeat transition order of A->B->D->C->A.

    Node HeartbeatOrder Value
    A 10
    B 20
    C 30
    D 25

    To use this parameter to change the heartbeat transmission order in a running NDB Cluster, you must first set HeartbeatOrder for each data node in the cluster in the global configuration (config.ini) file (or files). To cause the change to take effect, you must perform either of the following:

    • A complete shutdown and restart of the entire cluster.

    • 2 rolling restarts of the cluster in succession. All nodes must be restarted in the same order in both rolling restarts.

    You can use DUMP 908 to observe the effect of this parameter in the data node logs.

  • ConnectCheckIntervalDelay

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter enables connection checking between data nodes after one of them has failed heartbeat checks for 5 intervals of up to HeartbeatIntervalDbDb milliseconds.

    Such a data node that further fails to respond within an interval of ConnectCheckIntervalDelay milliseconds is considered suspect, and is considered dead after two such intervals. This can be useful in setups with known latency issues.

    The default value for this parameter is 0 (disabled).

  • TimeBetweenLocalCheckpoints

    Version (or later) NDB 8.0.13
    Type or units number of 4-byte words, as base-2 logarithm
    Default 20
    Range 0 - 31
    Restart Type N

    This parameter is an exception in that it does not specify a time to wait before starting a new local checkpoint; rather, it is used to ensure that local checkpoints are not performed in a cluster where relatively few updates are taking place. In most clusters with high update rates, it is likely that a new local checkpoint is started immediately after the previous one has been completed.

    The size of all write operations executed since the start of the previous local checkpoints is added. This parameter is also exceptional in that it is specified as the base-2 logarithm of the number of 4-byte words, so that the default value 20 means 4MB (4 × 220) of write operations, 21 would mean 8MB, and so on up to a maximum value of 31, which equates to 8GB of write operations.

    All the write operations in the cluster are added together. Setting TimeBetweenLocalCheckpoints to 6 or less means that local checkpoints are executed continuously without pause, independent of the cluster's workload.

  • TimeBetweenGlobalCheckpoints

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 2000
    Range 20 - 32000
    Restart Type N

    When a transaction is committed, it is committed in main memory in all nodes on which the data is mirrored. However, transaction log records are not flushed to disk as part of the commit. The reasoning behind this behavior is that having the transaction safely committed on at least two autonomous host machines should meet reasonable standards for durability.

    It is also important to ensure that even the worst of cases—a complete crash of the cluster—is handled properly. To guarantee that this happens, all transactions taking place within a given interval are put into a global checkpoint, which can be thought of as a set of committed transactions that has been flushed to disk. In other words, as part of the commit process, a transaction is placed in a global checkpoint group. Later, this group's log records are flushed to disk, and then the entire group of transactions is safely committed to disk on all computers in the cluster.

    In NDB 8.0.19 and later, it recommended when using solid-state disks (especially those employing NVMe) with Disk Data tables that you reduce this value. In such cases, you should also ensure that MaxDiskDataLatency is set to a proper level.

    This parameter defines the interval between global checkpoints. The default is 2000 milliseconds.

  • TimeBetweenGlobalCheckpointsTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 120000
    Range 10 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter defines the minimum timeout between global checkpoints. The default is 120000 milliseconds.

  • TimeBetweenEpochs

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 100
    Range 0 - 32000
    Restart Type N

    This parameter defines the interval between synchronization epochs for NDB Cluster Replication. The default value is 100 milliseconds.

    TimeBetweenEpochs is part of the implementation of micro-GCPs, which can be used to improve the performance of NDB Cluster Replication.

  • TimeBetweenEpochsTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 256000
    Restart Type N

    This parameter defines a timeout for synchronization epochs for NDB Cluster Replication. If a node fails to participate in a global checkpoint within the time determined by this parameter, the node is shut down. The default value is 0; in other words, the timeout is disabled.

    TimeBetweenEpochsTimeout is part of the implementation of micro-GCPs, which can be used to improve the performance of NDB Cluster Replication.

    The current value of this parameter and a warning are written to the cluster log whenever a GCP save takes longer than 1 minute or a GCP commit takes longer than 10 seconds.

    Setting this parameter to zero has the effect of disabling GCP stops caused by save timeouts, commit timeouts, or both. The maximum possible value for this parameter is 256000 milliseconds.

  • MaxBufferedEpochs

    Version (or later) NDB 8.0.13
    Type or units epochs
    Default 100
    Range 0 - 100000
    Restart Type N

    The number of unprocessed epochs by which a subscribing node can lag behind. Exceeding this number causes a lagging subscriber to be disconnected.

    The default value of 100 is sufficient for most normal operations. If a subscribing node does lag enough to cause disconnections, it is usually due to network or scheduling issues with regard to processes or threads. (In rare circumstances, the problem may be due to a bug in the NDB client.) It may be desirable to set the value lower than the default when epochs are longer.

    Disconnection prevents client issues from affecting the data node service, running out of memory to buffer data, and eventually shutting down. Instead, only the client is affected as a result of the disconnect (by, for example gap events in the binary log), forcing the client to reconnect or restart the process.

  • MaxBufferedEpochBytes

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 26214400
    Range 26214400 (0x01900000) - 4294967039 (0xFFFFFEFF)
    Restart Type N

    The total number of bytes allocated for buffering epochs by this node.

  • TimeBetweenInactiveTransactionAbortCheck

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 1000
    Range 1000 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Timeout handling is performed by checking a timer on each transaction once for every interval specified by this parameter. Thus, if this parameter is set to 1000 milliseconds, every transaction is checked for timing out once per second.

    The default value is 1000 milliseconds (1 second).

  • TransactionInactiveTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 4294967039 (0xFFFFFEFF)
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter states the maximum time that is permitted to lapse between operations in the same transaction before the transaction is aborted.

    The default for this parameter is 4G (also the maximum). For a real-time database that needs to ensure that no transaction keeps locks for too long, this parameter should be set to a relatively small value. Setting it to 0 means that the application never times out. The unit is milliseconds.

  • TransactionDeadlockDetectionTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 1200
    Range 50 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When a node executes a query involving a transaction, the node waits for the other nodes in the cluster to respond before continuing. This parameter sets the amount of time that the transaction can spend executing within a data node, that is, the time that the transaction coordinator waits for each data node participating in the transaction to execute a request.

    A failure to respond can occur for any of the following reasons:

    • The node is dead

    • The operation has entered a lock queue

    • The node requested to perform the action could be heavily overloaded.

    This timeout parameter states how long the transaction coordinator waits for query execution by another node before aborting the transaction, and is important for both node failure handling and deadlock detection.

    The default timeout value is 1200 milliseconds (1.2 seconds).

    The minimum for this parameter is 50 milliseconds.

  • DiskSyncSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 4M
    Range 32K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This is the maximum number of bytes to store before flushing data to a local checkpoint file. This is done to prevent write buffering, which can impede performance significantly. This parameter is not intended to take the place of TimeBetweenLocalCheckpoints.

    Note

    When ODirect is enabled, it is not necessary to set DiskSyncSize; in fact, in such cases its value is simply ignored.

    The default value is 4M (4 megabytes).

  • MaxDiskWriteSpeed

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 20M
    Range 1M - 1024G
    Restart Type S

    Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations when no restarts (by this data node or any other data node) are taking place in this NDB Cluster.

    For setting the maximum rate of disk writes allowed while this data node is restarting, use MaxDiskWriteSpeedOwnRestart. For setting the maximum rate of disk writes allowed while other data nodes are restarting, use MaxDiskWriteSpeedOtherNodeRestart. The minimum speed for disk writes by all LCPs and backup operations can be adjusted by setting MinDiskWriteSpeed.

  • MaxDiskWriteSpeedOtherNodeRestart

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 50M
    Range 1M - 1024G
    Restart Type S

    Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations when one or more data nodes in this NDB Cluster are restarting, other than this node.

    For setting the maximum rate of disk writes allowed while this data node is restarting, use MaxDiskWriteSpeedOwnRestart. For setting the maximum rate of disk writes allowed when no data nodes are restarting anywhere in the cluster, use MaxDiskWriteSpeed. The minimum speed for disk writes by all LCPs and backup operations can be adjusted by setting MinDiskWriteSpeed.

  • MaxDiskWriteSpeedOwnRestart

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 200M
    Range 1M - 1024G
    Restart Type S

    Set the maximum rate for writing to disk, in bytes per second, by local checkpoints and backup operations while this data node is restarting.

    For setting the maximum rate of disk writes allowed while other data nodes are restarting, use MaxDiskWriteSpeedOtherNodeRestart. For setting the maximum rate of disk writes allowed when no data nodes are restarting anywhere in the cluster, use MaxDiskWriteSpeed. The minimum speed for disk writes by all LCPs and backup operations can be adjusted by setting MinDiskWriteSpeed.

  • MinDiskWriteSpeed

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 10M
    Range 1M - 1024G
    Restart Type S

    Set the minimum rate for writing to disk, in bytes per second, by local checkpoints and backup operations.

    The maximum rates of disk writes allowed for LCPs and backups under various conditions are adjustable using the parameters MaxDiskWriteSpeed, MaxDiskWriteSpeedOwnRestart, and MaxDiskWriteSpeedOtherNodeRestart. See the descriptions of these parameters for more information.

  • ArbitrationTimeout

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 7500
    Range 10 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter specifies how long data nodes wait for a response from the arbitrator to an arbitration message. If this is exceeded, the network is assumed to have split.

    The default value is 7500 milliseconds (7.5 seconds).

  • Arbitration

    Version (or later) NDB 8.0.13
    Type or units enumeration
    Default Default
    Range Default, Disabled, WaitExternal
    Restart Type N

    The Arbitration parameter enables a choice of arbitration schemes, corresponding to one of 3 possible values for this parameter:

    • Default.  This enables arbitration to proceed normally, as determined by the ArbitrationRank settings for the management and API nodes. This is the default value.

    • Disabled.  Setting Arbitration = Disabled in the [ndbd default] section of the config.ini file to accomplishes the same task as setting ArbitrationRank to 0 on all management and API nodes. When Arbitration is set in this way, any ArbitrationRank settings are ignored.

    • WaitExternal.  The Arbitration parameter also makes it possible to configure arbitration in such a way that the cluster waits until after the time determined by ArbitrationTimeout has passed for an external cluster manager application to perform arbitration instead of handling arbitration internally. This can be done by setting Arbitration = WaitExternal in the [ndbd default] section of the config.ini file. For best results with the WaitExternal setting, it is recommended that ArbitrationTimeout be 2 times as long as the interval required by the external cluster manager to perform arbitration.

    Important

    This parameter should be used only in the [ndbd default] section of the cluster configuration file. The behavior of the cluster is unspecified when Arbitration is set to different values for individual data nodes.

  • RestartSubscriberConnectTimeout

    Version (or later) NDB 8.0.13
    Type or units ms
    Default 12000
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type S

    This parameter determines the time that a data node waits for subscribing API nodes to connect. Once this timeout expires, any missing API nodes are disconnected from the cluster. To disable this timeout, set RestartSubscriberConnectTimeout to 0.

    While this parameter is specified in milliseconds, the timeout itself is resolved to the next-greatest whole second.

Buffering and logging.  Several [ndbd] configuration parameters enable the advanced user to have more control over the resources used by node processes and to adjust various buffer sizes at need.

These buffers are used as front ends to the file system when writing log records to disk. If the node is running in diskless mode, these parameters can be set to their minimum values without penalty due to the fact that disk writes are faked by the NDB storage engine's file system abstraction layer.

  • UndoIndexBuffer

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 2M
    Range 1M - 4294967039 (0xFFFFFEFF)
    Restart Type N

    The UNDO index buffer, whose size is set by this parameter, is used during local checkpoints. The NDB storage engine uses a recovery scheme based on checkpoint consistency in conjunction with an operational REDO log. To produce a consistent checkpoint without blocking the entire system for writes, UNDO logging is done while performing the local checkpoint. UNDO logging is activated on a single table fragment at a time. This optimization is possible because tables are stored entirely in main memory.

    The UNDO index buffer is used for the updates on the primary key hash index. Inserts and deletes rearrange the hash index; the NDB storage engine writes UNDO log records that map all physical changes to an index page so that they can be undone at system restart. It also logs all active insert operations for each fragment at the start of a local checkpoint.

    Reads and updates set lock bits and update a header in the hash index entry. These changes are handled by the page-writing algorithm to ensure that these operations need no UNDO logging.

    This buffer is 2MB by default. The minimum value is 1MB, which is sufficient for most applications. For applications doing extremely large or numerous inserts and deletes together with large transactions and large primary keys, it may be necessary to increase the size of this buffer. If this buffer is too small, the NDB storage engine issues internal error code 677 (Index UNDO buffers overloaded).

    Important

    It is not safe to decrease the value of this parameter during a rolling restart.

  • UndoDataBuffer

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 16M
    Range 1M - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets the size of the UNDO data buffer, which performs a function similar to that of the UNDO index buffer, except the UNDO data buffer is used with regard to data memory rather than index memory. This buffer is used during the local checkpoint phase of a fragment for inserts, deletes, and updates.

    Because UNDO log entries tend to grow larger as more operations are logged, this buffer is also larger than its index memory counterpart, with a default value of 16MB.

    This amount of memory may be unnecessarily large for some applications. In such cases, it is possible to decrease this size to a minimum of 1MB.

    It is rarely necessary to increase the size of this buffer. If there is such a need, it is a good idea to check whether the disks can actually handle the load caused by database update activity. A lack of sufficient disk space cannot be overcome by increasing the size of this buffer.

    If this buffer is too small and gets congested, the NDB storage engine issues internal error code 891 (Data UNDO buffers overloaded).

    Important

    It is not safe to decrease the value of this parameter during a rolling restart.

  • RedoBuffer

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 32M
    Range 1M - 4294967039 (0xFFFFFEFF)
    Restart Type N

    All update activities also need to be logged. The REDO log makes it possible to replay these updates whenever the system is restarted. The NDB recovery algorithm uses a fuzzy checkpoint of the data together with the UNDO log, and then applies the REDO log to play back all changes up to the restoration point.

    RedoBuffer sets the size of the buffer in which the REDO log is written. The default value is 32MB; the minimum value is 1MB.

    If this buffer is too small, the NDB storage engine issues error code 1221 (REDO log buffers overloaded). For this reason, you should exercise care if you attempt to decrease the value of RedoBuffer as part of an online change in the cluster's configuration.

    ndbmtd allocates a separate buffer for each LDM thread (see ThreadConfig). For example, with 4 LDM threads, an ndbmtd data node actually has 4 buffers and allocates RedoBuffer bytes to each one, for a total of 4 * RedoBuffer bytes.

  • EventLogBufferSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 8192
    Range 0 - 64K
    Restart Type S

    Controls the size of the circular buffer used for NDB log events within data nodes.

Controlling log messages.  In managing the cluster, it is very important to be able to control the number of log messages sent for various event types to stdout. For each event category, there are 16 possible event levels (numbered 0 through 15). Setting event reporting for a given event category to level 15 means all event reports in that category are sent to stdout; setting it to 0 means that no event reports in that category are made.

By default, only the startup message is sent to stdout, with the remaining event reporting level defaults being set to 0. The reason for this is that these messages are also sent to the management server's cluster log.

An analogous set of levels can be set for the management client to determine which event levels to record in the cluster log.

  • LogLevelStartup

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 1
    Range 0 - 15
    Restart Type N

    The reporting level for events generated during startup of the process.

    The default level is 1.

  • LogLevelShutdown

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated as part of graceful shutdown of a node.

    The default level is 0.

  • LogLevelStatistic

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for statistical events such as number of primary key reads, number of updates, number of inserts, information relating to buffer usage, and so on.

    The default level is 0.

  • LogLevelCheckpoint

    Version (or later) NDB 8.0.13
    Type or units log level
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated by local and global checkpoints.

    The default level is 0.

  • LogLevelNodeRestart

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated during node restart.

    The default level is 0.

  • LogLevelConnection

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated by connections between cluster nodes.

    The default level is 0.

  • LogLevelError

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated by errors and warnings by the cluster as a whole. These errors do not cause any node failure but are still considered worth reporting.

    The default level is 0.

  • LogLevelCongestion

    Version (or later) NDB 8.0.13
    Type or units level
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated by congestion. These errors do not cause node failure but are still considered worth reporting.

    The default level is 0.

  • LogLevelInfo

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 15
    Restart Type N

    The reporting level for events generated for information about the general state of the cluster.

    The default level is 0.

  • MemReportFrequency

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter controls how often data node memory usage reports are recorded in the cluster log; it is an integer value representing the number of seconds between reports.

    Each data node's data memory and index memory usage is logged as both a percentage and a number of 32 KB pages of DataMemory, as set in the config.ini file. For example, if DataMemory is equal to 100 MB, and a given data node is using 50 MB for data memory storage, the corresponding line in the cluster log might look like this:

    2006-12-24 01:18:16 [MgmSrvr] INFO -- Node 2: Data usage is 50%(1280 32K pages of total 2560)
    

    MemReportFrequency is not a required parameter. If used, it can be set for all cluster data nodes in the [ndbd default] section of config.ini, and can also be set or overridden for individual data nodes in the corresponding [ndbd] sections of the configuration file. The minimum value—which is also the default value—is 0, in which case memory reports are logged only when memory usage reaches certain percentages (80%, 90%, and 100%), as mentioned in the discussion of statistics events in Section 23.5.3.2, “NDB Cluster Log Events”.

  • StartupStatusReportFrequency

    Version (or later) NDB 8.0.13
    Type or units seconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When a data node is started with the --initial, it initializes the redo log file during Start Phase 4 (see Section 23.5.4, “Summary of NDB Cluster Start Phases”). When very large values are set for NoOfFragmentLogFiles, FragmentLogFileSize, or both, this initialization can take a long time.You can force reports on the progress of this process to be logged periodically, by means of the StartupStatusReportFrequency configuration parameter. In this case, progress is reported in the cluster log, in terms of both the number of files and the amount of space that have been initialized, as shown here:

    2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 1: Local redo log file initialization status:
    #Total files: 80, Completed: 60
    #Total MBytes: 20480, Completed: 15557
    2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 2: Local redo log file initialization status:
    #Total files: 80, Completed: 60
    #Total MBytes: 20480, Completed: 15570
    

    These reports are logged each StartupStatusReportFrequency seconds during Start Phase 4. If StartupStatusReportFrequency is 0 (the default), then reports are written to the cluster log only when at the beginning and at the completion of the redo log file initialization process.

Data Node Debugging Parameters

The following parameters are intended for use during testing or debugging of data nodes, and not for use in production.

  • DictTrace

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default undefined
    Range 0 - 100
    Restart Type N

    It is possible to cause logging of traces for events generated by creating and dropping tables using DictTrace. This parameter is useful only in debugging NDB kernel code. DictTrace takes an integer value. 0 is the default, and means no logging is performed; 1 enables trace logging, and 2 enables logging of additional DBDICT debugging output.

  • WatchdogImmediateKill

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type S

    You can cause threads to be killed immediately whenever watchdog issues occur by enabling the WatchdogImmediateKill data node configuration parameter. This parameter should be used only when debugging or troubleshooting, to obtain trace files reporting exactly what was occurring the instant that execution ceased.

Backup parameters.  The [ndbd] parameters discussed in this section define memory buffers set aside for execution of online backups.

  • BackupDataBufferSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 16M
    Range 512K - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated Yes (in NDB 7.6)

    In creating a backup, there are two buffers used for sending data to the disk. The backup data buffer is used to fill in data recorded by scanning a node's tables. Once this buffer has been filled to the level specified as BackupWriteSize, the pages are sent to disk. While flushing data to disk, the backup process can continue filling this buffer until it runs out of space. When this happens, the backup process pauses the scan and waits until some disk writes have completed freeing up memory so that scanning may continue.

    The default value for this parameter is 16MB. The minimum is 512K.

  • BackupDiskWriteSpeedPct

    Version (or later) NDB 8.0.13
    Type or units percent
    Default 50
    Range 0 - 90
    Restart Type N

    During normal operation, data nodes attempt to maximize the disk write speed used for local checkpoints and backups while remaining within the bounds set by MinDiskWriteSpeed and MaxDiskWriteSpeed. Disk write throttling gives each LDM thread an equal share of the total budget. This allows parallel LCPs to take place without exceeding the disk I/O budget. Because a backup is executed by only one LDM thread, this effectively caused a budget cut, resulting in longer backup completion times, and—if the rate of change is sufficiently high—in failure to complete the backup when the backup log buffer fill rate is higher than the achievable write rate.

    This problem can be addressed by using the BackupDiskWriteSpeedPct configuration parameter, which takes a value in the range 0-90 (inclusive) which is interpreted as the percentage of the node's maximum write rate budget that is reserved prior to sharing out the remainder of the budget among LDM threads for LCPs. The LDM thread running the backup receives the whole write rate budget for the backup, plus its (reduced) share of the write rate budget for local checkpoints.

    The default value for this parameter is 50 (interpreted as 50%).

  • BackupLogBufferSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 16M
    Range 2M - 4294967039 (0xFFFFFEFF)
    Restart Type N

    The backup log buffer fulfills a role similar to that played by the backup data buffer, except that it is used for generating a log of all table writes made during execution of the backup. The same principles apply for writing these pages as with the backup data buffer, except that when there is no more space in the backup log buffer, the backup fails. For that reason, the size of the backup log buffer must be large enough to handle the load caused by write activities while the backup is being made. See Section 23.5.8.3, “Configuration for NDB Cluster Backups”.

    The default value for this parameter should be sufficient for most applications. In fact, it is more likely for a backup failure to be caused by insufficient disk write speed than it is for the backup log buffer to become full. If the disk subsystem is not configured for the write load caused by applications, the cluster is unlikely to be able to perform the desired operations.

    It is preferable to configure cluster nodes in such a manner that the processor becomes the bottleneck rather than the disks or the network connections.

    The default value for this parameter is 16MB.

  • BackupMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 32M
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated Yes (in NDB 7.4)

    This parameter is deprecated, and subject to removal in a future version of NDB Cluster. Any setting made for it is ignored.

  • BackupReportFrequency

    Version (or later) NDB 8.0.13
    Type or units seconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter controls how often backup status reports are issued in the management client during a backup, as well as how often such reports are written to the cluster log (provided cluster event logging is configured to permit it—see Logging and checkpointing). BackupReportFrequency represents the time in seconds between backup status reports.

    The default value is 0.

  • BackupWriteSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 256K
    Range 32K - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated Yes (in NDB 7.6)

    This parameter specifies the default size of messages written to disk by the backup log and backup data buffers.

    The default value for this parameter is 256KB.

  • BackupMaxWriteSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 1M
    Range 256K - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated Yes (in NDB 7.6)

    This parameter specifies the maximum size of messages written to disk by the backup log and backup data buffers.

    The default value for this parameter is 1MB.

  • CompressedBackup

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Enabling this parameter causes backup files to be compressed. The compression used is equivalent to gzip --fast, and can save 50% or more of the space required on the data node to store uncompressed backup files. Compressed backups can be enabled for individual data nodes, or for all data nodes (by setting this parameter in the [ndbd default] section of the config.ini file).

    Important

    You cannot restore a compressed backup to a cluster running a MySQL version that does not support this feature.

    The default value is 0 (disabled).

  • RequireEncryptedBackup

    Version (or later) NDB 8.0.22
    Type or units integer
    Default 0
    Range 0 - 1
    Restart Type N
    Added NDB 8.0.22

    If set to 1, backups must be encrypted. While it is possible to set this parameter for each data node individually, it is recommended that you set it in the [ndbd default] section of the config.ini global configuration file. For more information about performing encrypted backups, see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”.

    Added in NDB 8.0.22.

Note

The location of the backup files is determined by the BackupDataDir data node configuration parameter.

Additional requirements.  When specifying these parameters, the following relationships must hold true. Otherwise, the data node cannot start.

  • BackupDataBufferSize >= BackupWriteSize + 188KB

  • BackupLogBufferSize >= BackupWriteSize + 16KB

  • BackupMaxWriteSize >= BackupWriteSize

NDB Cluster Realtime Performance Parameters

The [ndbd] parameters discussed in this section are used in scheduling and locking of threads to specific CPUs on multiprocessor data node hosts.

Note

To make use of these parameters, the data node process must be run as system root.

  • BuildIndexThreads

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 128
    Range 0 - 128
    Restart Type S

    This parameter determines the number of threads to create when rebuilding ordered indexes during a system or node start, as well as when running ndb_restore --rebuild-indexes. It is supported only when there is more than one fragment for the table per data node (for example, when COMMENT="NDB_TABLE=PARTITION_BALANCE=FOR_RA_BY_LDM_X_2" is used with CREATE TABLE).

    Setting this parameter to 0 (the default) disables multithreaded building of ordered indexes.

    This parameter is supported when using ndbd or ndbmtd.

    You can enable multithreaded builds during data node initial restarts by setting the TwoPassInitialNodeRestartCopy data node configuration parameter to TRUE.

  • LockExecuteThreadToCPU

    Version (or later) NDB 8.0.13
    Type or units set of CPU IDs
    Default 0
    Range ...
    Restart Type N

    When used with ndbd, this parameter (now a string) specifies the ID of the CPU assigned to handle the NDBCLUSTER execution thread. When used with ndbmtd, the value of this parameter is a comma-separated list of CPU IDs assigned to handle execution threads. Each CPU ID in the list should be an integer in the range 0 to 65535 (inclusive).

    The number of IDs specified should match the number of execution threads determined by MaxNoOfExecutionThreads. However, there is no guarantee that threads are assigned to CPUs in any given order when using this parameter. You can obtain more finely-grained control of this type using ThreadConfig.

    LockExecuteThreadToCPU has no default value.

  • LockMaintThreadsToCPU

    Version (or later) NDB 8.0.13
    Type or units CPU ID
    Default 0
    Range 0 - 64K
    Restart Type N

    This parameter specifies the ID of the CPU assigned to handle NDBCLUSTER maintenance threads.

    The value of this parameter is an integer in the range 0 to 65535 (inclusive). There is no default value.

  • Numa

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 1
    Range ...
    Restart Type N

    This parameter determines whether Non-Uniform Memory Access (NUMA) is controlled by the operating system or by the data node process, whether the data node uses ndbd or ndbmtd. By default, NDB attempts to use an interleaved NUMA memory allocation policy on any data node where the host operating system provides NUMA support.

    Setting Numa = 0 means that the datanode process does not itself attempt to set a policy for memory allocation, and permits this behavior to be determined by the operating system, which may be further guided by the separate numactl tool. That is, Numa = 0 yields the system default behavior, which can be customised by numactl. For many Linux systems, the system default behavior is to allocate socket-local memory to any given process at allocation time. This can be problematic when using ndbmtd; this is because nbdmtd allocates all memory at startup, leading to an imbalance, giving different access speeds for different sockets, especially when locking pages in main memory.

    Setting Numa = 1 means that the data node process uses libnuma to request interleaved memory allocation. (This can also be accomplished manually, on the operating system level, using numactl.) Using interleaved allocation in effect tells the data node process to ignore non-uniform memory access but does not attempt to take any advantage of fast local memory; instead, the data node process tries to avoid imbalances due to slow remote memory. If interleaved allocation is not desired, set Numa to 0 so that the desired behavior can be determined on the operating system level.

    The Numa configuration parameter is supported only on Linux systems where libnuma.so is available.

  • RealtimeScheduler

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Setting this parameter to 1 enables real-time scheduling of data node threads.

    The default is 0 (scheduling disabled).

  • SchedulerExecutionTimer

    Version (or later) NDB 8.0.13
    Type or units µs
    Default 50
    Range 0 - 11000
    Restart Type N

    This parameter specifies the time in microseconds for threads to be executed in the scheduler before being sent. Setting it to 0 minimizes the response time; to achieve higher throughput, you can increase the value at the expense of longer response times.

    The default is 50 μsec, which our testing shows to increase throughput slightly in high-load cases without materially delaying requests.

  • SchedulerResponsiveness

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 5
    Range 0 - 10
    Restart Type S

    Set the balance in the NDB scheduler between speed and throughput. This parameter takes an integer whose value is in the range 0-10 inclusive, with 5 as the default. Higher values provide better response times relative to throughput. Lower values provide increased throughput at the expense of longer response times.

  • SchedulerSpinTimer

    Version (or later) NDB 8.0.13
    Type or units µs
    Default 0
    Range 0 - 500
    Restart Type N

    This parameter specifies the time in microseconds for threads to be executed in the scheduler before sleeping.

    Starting with NDB 8.0.20, if SpinMethod is set, any setting for this parameter is ignored.

  • SpinMethod

    Version (or later) NDB 8.0.20
    Type or units enumeration
    Default StaticSpinning
    Range CostBasedSpinning, LatencyOptimisedSpinning, DatabaseMachineSpinning, StaticSpinning
    Restart Type N
    Added NDB 8.0.20

    This parameter provides a simple interface to control adaptive spinning on data nodes, with four possible values furnishing presets for spin parameter values, as shown in the following list:

    1. StaticSpinning (default): Sets EnableAdaptiveSpinning to false and SchedulerSpinTimer to 0. (SetAllowedSpinOverhead is not relevant in this case.)

    2. CostBasedSpinning: Sets EnableAdaptiveSpinning to true, SchedulerSpinTimer to 100, and SetAllowedSpinOverhead to 200.

    3. LatencyOptimisedSpinning: Sets EnableAdaptiveSpinning to true, SchedulerSpinTimer to 200, and SetAllowedSpinOverhead to 1000.

    4. DatabaseMachineSpinning: Sets EnableAdaptiveSpinning to true, SchedulerSpinTimer to 500, and SetAllowedSpinOverhead to 10000. This is intended for use in cases where threads own their own CPUs.

    The spin parameters modified by SpinMethod are described in the following list:

    • SchedulerSpinTimer: This is the same as the data node configuration parameter of that name. The setting applied to this parameter by SpinMethod overrides any value set in the config.ini file.

    • EnableAdaptiveSpinning: Enables or disables adaptive spinning. Disabling it causes spinning to be performed without making any checks for CPU resources. This parameter cannot be set directly in the cluster configuration file, and under most circumstances should not need to be, but can be enabled directly using DUMP 104004 1 or disabled with DUMP 104004 0 in the ndb_mgm management client.

    • SetAllowedSpinOverhead: Sets the amount of CPU time to allow for gaining latency. This parameter cannot be set directly in the config.ini file. In most cases, the setting applied by SpinMethod should be satisfactory, but if it is necessary to change it directly, you can use DUMP 104002 overhead to do so, where overhead is a value ranging from 0 to 10000, inclusive; see the description of the indicated DUMP command for details.

    On platforms lacking usable spin instructions, such as PowerPC and some SPARC platforms, spin time is set to 0 in all situations, and values for SpinMethod other than StaticSpinning are ignored.

  • TwoPassInitialNodeRestartCopy

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default true
    Range true, false
    Restart Type N

    Multithreaded building of ordered indexes can be enabled for initial restarts of data nodes by setting this configuration parameter to true (the default value), which enables two-pass copying of data during initial node restarts.

    You must also set BuildIndexThreads to a nonzero value.

Multi-Threading Configuration Parameters (ndbmtd).  ndbmtd runs by default as a single-threaded process and must be configured to use multiple threads, using either of two methods, both of which require setting configuration parameters in the config.ini file. The first method is simply to set an appropriate value for the MaxNoOfExecutionThreads configuration parameter. A second method, makes it possible to set up more complex rules for ndbmtd multithreading using ThreadConfig. The next few paragraphs provide information about these parameters and their use with multithreaded data nodes.

Note

A backup using parallelism on the data nodes requires that multiple LDMs are in use on all data nodes in the cluster prior to taking the backup. For more information, see Section 23.5.8.5, “Taking an NDB Backup with Parallel Data Nodes”, as well as Section 23.4.23.3, “Restoring from a backup taken in parallel”.

  • AutomaticThreadConfig

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type IS
    Added NDB 8.0.23

    When set to 1, enables automatic thread configuration employing the number of CPUs available to a data node taking into account any limits set by taskset, numactl, virtual machines, Docker, and other such means of controlling which CPUs are available to a given application (on Windows platforms, automatic thread configuration uses all CPUs which are online); alternatively, you can set NumCPUs to the desired number of CPUs (up to 1024, the maximum number of CPUs that can be handled by automatic thread configuration). Any settings for ThreadConfig and MaxNoOfExecutionThreads are ignored.

  • ClassicFragmentation

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default true
    Range true, false
    Restart Type N
    Added NDB 8.0.23

    When enabled (set to true), NDB uses flexible distribution of table fragents among LDMs. This means that the default number of partitions per node is equal to PartitionsPerNode, rather than to the minimum number of LDM threads per data node, and that each table has a number of partitions equal to 4 (the default for PartitionsPerNode) times the number of data nodes.

    For new clusters for which a downgrade to NDB 8.0.22 or earlier is never expected to occur, setting ClassicFragmentation to false when first setting up the cluster is preferable; this ensures that all partitions are spread out evenly between all LDMs.

  • MaxNoOfExecutionThreads

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 2
    Range 2 - 72
    Restart Type IS

    This parameter directly controls the number of execution threads used by ndbmtd, up to a maximum of 72. Although this parameter is set in [ndbd] or [ndbd default] sections of the config.ini file, it is exclusive to ndbmtd and does not apply to ndbd.

    Setting MaxNoOfExecutionThreads sets the number of threads for each type as determined by a matrix in the file storage/ndb/src/kernel/vm/mt_thr_config.cpp. This table shows these numbers of threads for possible values of MaxNoOfExecutionThreads.

    Table 23.12 MaxNoOfExecutionThreads values and the corresponding number of threads by thread type (LQH, TC, Send, Receive).

    MaxNoOfExecutionThreads Value LDM Threads TC Threads Send Threads Receive Threads
    0 .. 3 1 0 0 1
    4 .. 6 2 0 0 1
    7 .. 8 4 0 0 1
    9 4 2 0 1
    10 4 2 1 1
    11 4 3 1 1
    12 6 2 1 1
    13 6 3 1 1
    14 6 3 1 2
    15 6 3 2 2
    16 8 3 1 2
    17 8 4 1 2
    18 8 4 2 2
    19 8 5 2 2
    20 10 4 2 2
    21 10 5 2 2
    22 10 5 2 3
    23 10 6 2 3
    24 12 5 2 3
    25 12 6 2 3
    26 12 6 3 3
    27 12 7 3 3
    28 12 7 3 4
    29 12 8 3 4
    30 12 8 4 4
    31 12 9 4 4
    32 16 8 3 3
    33 16 8 3 4
    34 16 8 4 4
    35 16 9 4 4
    36 16 10 4 4
    37 16 10 4 5
    38 16 11 4 5
    39 16 11 5 5
    40 20 10 4 4
    41 20 10 4 5
    42 20 11 4 5
    43 20 11 5 5
    44 20 12 5 5
    45 20 12 5 6
    46 20 13 5 6
    47 20 13 6 6
    48 24 12 5 5
    49 24 12 5 6
    50 24 13 5 6
    51 24 13 6 6
    52 24 14 6 6
    53 24 14 6 7
    54 24 15 6 7
    55 24 15 7 7
    56 24 16 7 7
    57 24 16 7 8
    58 24 17 7 8
    59 24 17 8 8
    60 24 18 8 8
    61 24 18 8 9
    62 24 19 8 9
    63 24 19 9 9
    64 32 16 7 7
    65 32 16 7 8
    66 32 17 7 8
    67 32 17 8 8
    68 32 18 8 8
    69 32 18 8 9
    70 32 19 8 9
    71 32 20 8 9
    72 32 20 8 10

    There is always one SUMA (replication) thread.

    NoOfFragmentLogParts should be set equal to the number of LDM threads used by ndbmtd, as determined by the setting for this parameter. This ratio should not be any greater than 4:1; a configuration in which this is the case is specifically disallowed.

    The number of LDM threads also determines the number of partitions used by an NDB table that is not explicitly partitioned; this is the number of LDM threads times the number of data nodes in the cluster. (If ndbd is used on the data nodes rather than ndbmtd, then there is always a single LDM thread; in this case, the number of partitions created automatically is simply equal to the number of data nodes. See Section 23.1.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”, for more information.

    Adding large tablespaces for Disk Data tables when using more than the default number of LDM threads may cause issues with resource and CPU usage if the disk page buffer is insufficiently large; see the description of the DiskPageBufferMemory configuration parameter, for more information.

    The thread types are described later in this section (see ThreadConfig).

    Setting this parameter outside the permitted range of values causes the management server to abort on startup with the error Error line number: Illegal value value for parameter MaxNoOfExecutionThreads.

    For MaxNoOfExecutionThreads, a value of 0 or 1 is rounded up internally by NDB to 2, so that 2 is considered this parameter's default and minimum value.

    MaxNoOfExecutionThreads is generally intended to be set equal to the number of CPU threads available, and to allocate a number of threads of each type suitable to typical workloads. It does not assign particular threads to specified CPUs. For cases where it is desirable to vary from the settings provided, or to bind threads to CPUs, you should use ThreadConfig instead, which allows you to allocate each thread directly to a desired type, CPU, or both.

    The multithreaded data node process always spawns, at a minimum, the threads listed here:

    • 1 local query handler (LDM) thread

    • 1 receive thread

    • 1 subscription manager (SUMA or replication) thread

    For a MaxNoOfExecutionThreads value of 8 or less, no TC threads are created, and TC handling is instead performed by the main thread.

    Changing the number of LDM threads normally requires a system restart, whether it is changed using this parameter or ThreadConfig, but it is possible to effect the change using a node initial restart (NI) provided the following two conditions are met:

    • Each LDM thread handles a maximum of 8 fragments, and

    • The total number of table fragments is an integer multiple of the number of LDM threads.

    In NDB 8.0, an initial restart is not required to effect a change in this parameter, as it was in some older versions of NDB Cluster.

  • NoOfFragmentLogParts

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 4
    Range 4, 6, 8, 10, 12, 16, 20, 24, 32
    Restart Type IN

    Set the number of log file groups for redo logs belonging to this ndbmtd. The value of this parameter should be set equal to the number of LDM threads used by ndbmtd as determined by the setting for MaxNoOfExecutionThreads. A configuration using more than 4 redo log parts per LDM is disallowed.

    See the description of MaxNoOfExecutionThreads for more information.

  • NumCPUs

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 1024
    Restart Type IS
    Added NDB 8.0.23

    Cause automatic thread configuration to use only this many CPUs. Has no effect if AutomaticThreadConfig is not enabled.

  • PartitionsPerNode

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 2
    Range 1 - 32
    Restart Type N
    Added NDB 8.0.23

    Sets the number of partitions used on each node when creating a new NDB table. This makes it possible to avoid splitting up tables into too an excessive number of partitions when the number of local data managers (LDMs) grows high.

    While it is possible to set this parameter to different values on different data nodes and there are no known issues with doing so, there is also not likely to be any advantage in doing so, and so it is recommended simply to set it once, for all data nodes, in the [ndbd default] section of the global config.ini file.

  • ThreadConfig

    Version (or later) NDB 8.0.13
    Type or units string
    Default ''
    Range ...
    Restart Type IS

    This parameter is used with ndbmtd to assign threads of different types to different CPUs. Its value is a string whose format has the following syntax:

    ThreadConfig := entry[,entry[,...]]
    
    entry := type={param[,param[,...]]}
    
    type (NDB 8.0.22 and earlier) := ldm | main | recv | send | rep | io | tc | watchdog | idxbld
    
    type (NDB 8.0.23 and later) := ldm | query | recover | main | recv | send | rep | io | tc | watchdog | idxbld
    
    param := count=number
      | cpubind=cpu_list
      | cpuset=cpu_list
      | spintime=number
      | realtime={0|1}
      | nosend={0|1}
      | thread_prio={0..10}
      | cpubind_exclusive=cpu_list
      | cpuset_exclusive=cpu_list
    

    The curly braces ({...}) surrounding the list of parameters are required, even if there is only one parameter in the list.

    A param (parameter) specifies any or all of the following information:

    • The number of threads of the given type (count).

    • The set of CPUs to which the threads of the given type are to be nonexclusively bound. This is determined by either one of cpubind or cpuset). cpubind causes each thread to be bound (nonexclusively) to a CPU in the set; cpuset means that each thread is bound (nonexclusively) to the set of CPUs specified.

      On Solaris, you can instead specify a set of CPUs to which the threads of the given type are to be bound exclusively. cpubind_exclusive causes each thread to be bound exclusively to a CPU in the set; cpuset_exclsuive means that each thread is bound exclusively to the set of CPUs specified.

      Only one of cpubind, cpuset, cpubind_exclusive, or cpuset_exclusive can be provided in a single configuration.

    • spintime determines the wait time in microseconds the thread spins before going to sleep.

      The default value for spintime is the value of the SchedulerSpinTimer data node configuration parameter.

      spintime does not apply to I/O threads, watchdog, or offline index build threads, and so cannot be set for these thread types.

    • realtime can be set to 0 or 1. If it is set to 1, the threads run with real-time priority. This also means that thread_prio cannot be set.

      The realtime parameter is set by default to the value of the RealtimeScheduler data node configuration parameter.

      realtime cannot be set for offline index build threads.

    • By setting nosend to 1, you can prevent a main, ldm, rep, or tc thread from assisting the send threads. This parameter is 0 by default, and cannot be used with other types of threads.

    • thread_prio is a thread priority level that can be set from 0 to 10, with 10 representing the greatest priority. The default is 5. The precise effects of this parameter are platform-specific, and are described later in this section.

      The thread priority level cannot be set for offline index build threads.

    thread_prio settings and effects by platform.  The implementation of thread_prio differs between Linux/FreeBSD, Solaris, and Windows. In the following list, we discuss its effects on each of these platforms in turn:

    • Linux and FreeBSD: We map thread_prio to a value to be supplied to the nice system call. Since a lower niceness value for a process indicates a higher process priority, increasing thread_prio has the effect of lowering the nice value.

      Table 23.13 Mapping of thread_prio to nice values on Linux and FreeBSD

      thread_prio value nice value
      0 19
      1 16
      2 12
      3 8
      4 4
      5 0
      6 -4
      7 -8
      8 -12
      9 -16
      10 -20

      Some operating systems may provide for a maximum process niceness level of 20, but this is not supported by all targeted versions; for this reason, we choose 19 as the maximum nice value that can be set.

    • Solaris: Setting thread_prio on Solaris sets the Solaris FX priority, with mappings as shown in the following table:

      Table 23.14 Mapping of thread_prio to FX priority on Solaris

      thread_prio value Solaris FX priority
      0 15
      1 20
      2 25
      3 30
      4 35
      5 40
      6 45
      7 50
      8 55
      9 59
      10 60

      A thread_prio setting of 9 is mapped on Solaris to the special FX priority value 59, which means that the operating system also attempts to force the thread to run alone on its own CPU core.

    • Windows: We map thread_prio to a Windows thread priority value passed to the Windows API SetThreadPriority() function. This mapping is shown in the following table:

      Table 23.15 Mapping of thread_prio to Windows thread priority

      thread_prio value Windows thread priority
      0 - 1 THREAD_PRIORITY_LOWEST
      2 - 3 THREAD_PRIORITY_BELOW_NORMAL
      4 - 5 THREAD_PRIORITY_NORMAL
      6 - 7 THREAD_PRIORITY_ABOVE_NORMAL
      8 - 10 THREAD_PRIORITY_HIGHEST

    The type attribute represents an NDB thread type. The thread types supported, and the range of permitted count values for each, are provided in the following list:

    • ldm: Local query handler (DBLQH kernel block) that handles data. The more LDM threads that are used, the more highly partitioned the data becomes. Each LDM thread maintains its own sets of data and index partitions, as well as its own redo log. Prior to NDB 8.0.23, the value set for ldm must be one of the values 1, 2, 4, 6, 8, 12, 16, 24, or 32. In NDB 8.0.23 and later, it is possible to set ldm to any value in the range 1 to 332 inclusive; it also becomes possible to set it to 0, provided that main, rep, and tc are also 0, and that recv is set to 1; doing this causes ndbmtd to emulate ndbd.

      Changing the number of LDM threads normally requires a system restart to be effective and safe for cluster operations; this requirement is relaxed in certain cases, as explained later in this section. This is also true when this is done using MaxNoOfExecutionThreads.

      Adding large tablespaces (hundreds of gigabytes or more) for Disk Data tables when using more than the default number of LDMs may cause issues with resource and CPU usage if DiskPageBufferMemory is not sufficiently large.

    • query (Added in NDB 8.0.23): A query thread is tied to an LDM and together with it forms an LDM group; acts only on READ COMMITTED queries. The number of query threads must be set to 0, 1, 2, or 3 times the number of LDM threads. Query threads are not used, unless this is overridden by setting query to a nonzero value, or by enabling the AutomaticThreadConfig parameter, in which case LDMs behave as they did prior to NDB 8.0.23.

      A query thread also acts as a recovery thread (see next item), although the reverse is not true.

      Changing the number of query threads requires a node restart.

    • recover (Added in NDB 8.0.23): A recovery thread restores data from a fragment as part of an LCP.

      Changing the number of recovery threads requires a node restart.

    • tc: Transaction coordinator thread (DBTC kernel block) containing the state of an ongoing transaction. In NDB 8.0.23 and later, the maximum number of TC threads is 128; previously, this was 32.

      Optimally, every new transaction can be assigned to a new TC thread. In most cases 1 TC thread per 2 LDM threads is sufficient to guarantee that this can happen. In cases where the number of writes is relatively small when compared to the number of reads, it is possible that only 1 TC thread per 4 LQH threads is required to maintain transaction states. Conversely, in applications that perform a great many updates, it may be necessary for the ratio of TC threads to LDM threads to approach 1 (for example, 3 TC threads to 4 LDM threads).

      Setting tc to 0 causes TC handling to be done by the main thread. In most cases, this is effectively the same as setting it to 1.

      Range: 0-64 (NDB 8.0.22 and earlier: 0 - 32)

    • main: Data dictionary and transaction coordinator (DBDIH and DBTC kernel blocks), providing schema management. Prior to NDB 8.0.23, this was always handled by a single dedicated thread, beginning ith NDB 8.0.23, it is also possible to specify zero or two main threads.

      Range:

      • NDB 8.0.22 and earlier: 1 only.

        NDB 8.0.23 and later: 0-2.

        Setting main to 0 and rep to 1 causes the main blocks to be placed into the rep thread; the combined thread is shown in the ndbinfo.threads table as main_rep. This is effectively the same as setting rep equal to 1 and main equal to 0.

        It is also possible to set both main and rep to 0, in which case both threads are placed in the first recv thread; the resulting combined thread is named main_rep_recv in the threads table.

    • recv: Receive thread (CMVMI kernel block). Each receive thread handles one or more sockets for communicating with other nodes in an NDB Cluster, with one socket per node. NDB Cluster supports multiple receive threads; the maximum is 16 such threads.

      Range:

      • NDB 8.0.22 and earlier: 1 - 16

      • NDB 8.0.23 and later: 1 - 64

    • send: Send thread (CMVMI kernel block). To increase throughput, it is possible to perform sends from one or more separate, dedicated threads (maximum 8).

      In NDB 8.0.20 and later, due to changes in the multithreading implementation, using many send threads can have an adverse effect on scalability.

      Previously, all threads handled their own sending directly; this can still be made to happen by setting the number of send threads to 0 (this also happens when MaxNoOfExecutionThreads is set less than 10). While doing so can have an adeverse impact on throughput, it can also in some cases provide decreased latency.

      Range:

      • NDB 8.0.22 and earlier: 0 - 16

      • NDB 8.0.23 and later: 0 - 64

    • rep: Replication thread (SUMA kernel block). Prior to NDB 8.0.23, asynchronous replication operations are always handled by a single, dedicated thread. Beginning with NDB 8.0.23, this thread can be combined with the main thread (see range information).

      Range:

      • NDB 8.0.22 and earlier: 1 only.

      • NDB 8.0.23 and later: 0-1.

        Setting rep to 0 and main to 1 causes the rep blocks to be placed into the main thread; the combined thread is shown in the ndbinfo.threads table as main_rep. This is effectively the same as setting main equal to 1 and rep equal to 0.

        It is also possible to set both main and rep to 0, in which case both threads are placed in the first recv thread; the resulting combined thread is named main_rep_recv in the threads table.

    • io: File system and other miscellaneous operations. These are not demanding tasks, and are always handled as a group by a single, dedicated I/O thread.

      Range: 1 only.

    • watchdog: Parameters settings associated with this type are actually applied to several threads, each having a specific use. These threads include the SocketServer thread, which receives connection setups from other nodes; the SocketClient thread, which attempts to set up connections to other nodes; and the thread watchdog thread that checks that threads are progressing.

      Range: 1 only.

    • idxbld: Offline index build threads. Unlike the other thread types listed previously, which are permanent, these are temporary threads which are created and used only during node or system restarts, or when running ndb_restore --rebuild-indexes. They may be bound to CPU sets which overlap with CPU sets bound to permanent thread types.

      thread_prio, realtime, and spintime values cannot be set for offline index build threads. In addition, count is ignored for this type of thread.

      If idxbld is not specified, the default behavior is as follows:

      • Offline index build threads are not bound if the I/O thread is also not bound, and these threads use any available cores.

      • If the I/O thread is bound, then the offline index build threads are bound to the entire set of bound threads, due to the fact that there should be no other tasks for these threads to perform.

      Range: 0 - 1.

    Changing ThreadCOnfig normally requires a system initial restart, but this requirement can be relaxed under certain cirumstances:

    • If, following the change, the number of LDM threads remains the same as before, nothing more than a simple node restart (rolling restart, or N) is required to implement the change.

    • Otherwise (that is, if the number of LDM threads changes), it is still possible to effect the change using a node initial restart (NI) provided the following two conditions are met:

      1. Each LDM thread handles a maximum of 8 fragments, and

      2. The total number of table fragments is an integer multiple of the number of LDM threads.

    In any other case, a system initial restart is needed to change this parameter.

    NDB can distinguish between thread types by both of the following criteria:

    • Whether the thread is an execution thread. Threads of type main, ldm, query (NDB 8.0.23 and later), recv, rep, tc, and send are execution threads; io, recover (NDB 8.0.23 and later), watchdog, and idxbld threads are not considered execution threads.

    • Whether the allocation of threads to a given task is permanent or temporary. Currently all thread types except idxbld are considered permanent; idxbld threads are regarded as temporary threads.

    Simple examples:

    # Example 1.
    
    ThreadConfig=ldm={count=2,cpubind=1,2},main={cpubind=12},rep={cpubind=11}
    
    # Example 2.
    
    Threadconfig=main={cpubind=0},ldm={count=4,cpubind=1,2,5,6},io={cpubind=3}
    

    It is usually desirable when configuring thread usage for a data node host to reserve one or more number of CPUs for operating system and other tasks. Thus, for a host machine with 24 CPUs, you might want to use 20 CPU threads (leaving 4 for other uses), with 8 LDM threads, 4 TC threads (half the number of LDM threads), 3 send threads, 3 receive threads, and 1 thread each for schema management, asynchronous replication, and I/O operations. (This is almost the same distribution of threads used when MaxNoOfExecutionThreads is set equal to 20.) The following ThreadConfig setting performs these assignments, additionally binding all of these threads to specific CPUs:

    ThreadConfig=ldm{count=8,cpubind=1,2,3,4,5,6,7,8},main={cpubind=9},io={cpubind=9}, \
    rep={cpubind=10},tc{count=4,cpubind=11,12,13,14},recv={count=3,cpubind=15,16,17}, \
    send{count=3,cpubind=18,19,20}
    

    It should be possible in most cases to bind the main (schema management) thread and the I/O thread to the same CPU, as we have done in the example just shown.

    The following example incorporates groups of CPUs defined using both cpuset and cpubind, as well as use of thread prioritization.

    ThreadConfig=ldm={count=4,cpuset=0-3,thread_prio=8,spintime=200}, \
    ldm={count=4,cpubind=4-7,thread_prio=8,spintime=200}, \
    tc={count=4,cpuset=8-9,thread_prio=6},send={count=2,thread_prio=10,cpubind=10-11}, \
    main={count=1,cpubind=10},rep={count=1,cpubind=11}
    

    In this case we create two LDM groups; the first uses cpubind and the second uses cpuset. thread_prio and spintime are set to the same values for each group. This means there are eight LDM threads in total. (You should ensure that NoOfFragmentLogParts is also set to 8.) The four TC threads use only two CPUs; it is possible when using cpuset to specify fewer CPUs than threads in the group. (This is not true for cpubind.) The send threads use two threads using cpubind to bind these threads to CPUs 10 and 11. The main and rep threads can reuse these CPUs.

    This example shows how ThreadConfig and NoOfFragmentLogParts might be set up for a 24-CPU host with hyperthreading, leaving CPUs 10, 11, 22, and 23 available for operating system functions and interrupts:

    NoOfFragmentLogParts=10
    ThreadConfig=ldm={count=10,cpubind=0-4,12-16,thread_prio=9,spintime=200}, \
    tc={count=4,cpuset=6-7,18-19,thread_prio=8},send={count=1,cpuset=8}, \
    recv={count=1,cpuset=20},main={count=1,cpuset=9,21},rep={count=1,cpuset=9,21}, \
    io={count=1,cpuset=9,21,thread_prio=8},watchdog={count=1,cpuset=9,21,thread_prio=9}
    

    The next few examples include settings for idxbld. The first two of these demonstrate how a CPU set defined for idxbld can overlap those specified for other (permanent) thread types, the first using cpuset and the second using cpubind:

    ThreadConfig=main,ldm={count=4,cpuset=1-4},tc={count=4,cpuset=5,6,7}, \
    io={cpubind=8},idxbld={cpuset=1-8}
    
    ThreadConfig=main,ldm={count=1,cpubind=1},idxbld={count=1,cpubind=1}
    

    The next example specifies a CPU for the I/O thread, but not for the index build threads:

    ThreadConfig=main,ldm={count=4,cpuset=1-4},tc={count=4,cpuset=5,6,7}, \
    io={cpubind=8}
    

    Since the ThreadConfig setting just shown locks threads to eight cores numbered 1 through 8, it is equivalent to the setting shown here:

    ThreadConfig=main,ldm={count=4,cpuset=1-4},tc={count=4,cpuset=5,6,7}, \
    io={cpubind=8},idxbld={cpuset=1,2,3,4,5,6,7,8}
    

    In order to take advantage of the enhanced stability that the use of ThreadConfig offers, it is necessary to insure that CPUs are isolated, and that they not subject to interrupts, or to being scheduled for other tasks by the operating system. On many Linux systems, you can do this by setting IRQBALANCE_BANNED_CPUS in /etc/sysconfig/irqbalance to 0xFFFFF0, and by using the isolcpus boot option in grub.conf. For specific information, see your operating system or platform documentation.

Disk Data Configuration Parameters.  Configuration parameters affecting Disk Data behavior include the following:

  • DiskPageBufferEntries

    Version (or later) NDB 8.0.13
    Type or units 32K pages
    Default 10
    Range 1 - 1000
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units bytes
    Default 64MB
    Range 4MB - 16TB
    Restart Type N

    This is the number of page entries (page references) to allocate. It is specified as a number of 32K pages in DiskPageBufferMemory. The default is sufficient for most cases but you may need to increase the value of this parameter if you encounter problems with very large transactions on Disk Data tables. Each page entry requires approximately 100 bytes.

  • DiskPageBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 64M
    Range 4M - 1T
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units bytes
    Default 64M
    Range 4M - 16T
    Restart Type N

    This determines the amount of space used for caching pages on disk, and is set in the [ndbd] or [ndbd default] section of the config.ini file.

    Note

    Previously, this paraeter was specified as a number of 32 KB pages. Beginning with NDB 8.0.19, it is specified as a number of bytes.

    If the value for DiskPageBufferMemory is set too low in conjunction with using more than the default number of LDM threads in ThreadConfig (for example {ldm=6...}), problems can arise when trying to add a large (for example 500G) data file to a disk-based NDB table, wherein the process takes indefinitely long while occupying one of the CPU cores.

    This is due to the fact that, as part of adding a data file to a tablespace, extent pages are locked into memory in an extra PGMAN worker thread, for quick metadata access. When adding a large file, this worker has insufficient memory for all of the data file metadata. In such cases, you should either increase DiskPageBufferMemory, or add smaller tablespace files. You may also need to adjust DiskPageBufferEntries.

    You can query the ndbinfo.diskpagebuffer table to help determine whether the value for this parameter should be increased to minimize unnecessary disk seeks. See Section 23.5.14.27, “The ndbinfo diskpagebuffer Table”, for more information.

  • SharedGlobalMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 128M
    Range 0 - 64T
    Restart Type N

    This parameter determines the amount of memory that is used for log buffers, disk operations (such as page requests and wait queues), and metadata for tablespaces, log file groups, UNDO files, and data files. The shared global memory pool also provides memory used for satisfying the memory requirements of the UNDO_BUFFER_SIZE option used with CREATE LOGFILE GROUP and ALTER LOGFILE GROUP statements, including any default value implied for this options by the setting of the InitialLogFileGroup data node configuration parameter. SharedGlobalMemory can be set in the [ndbd] or [ndbd default] section of the config.ini configuration file, and is measured in bytes.

    The default value is 128M.

  • DiskIOThreadPool

    Version (or later) NDB 8.0.13
    Type or units threads
    Default 2
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter determines the number of unbound threads used for Disk Data file access. Before DiskIOThreadPool was introduced, exactly one thread was spawned for each Disk Data file, which could lead to performance issues, particularly when using very large data files. With DiskIOThreadPool, you can—for example—access a single large data file using several threads working in parallel.

    This parameter applies to Disk Data I/O threads only.

    The optimum value for this parameter depends on your hardware and configuration, and includes these factors:

    • Physical distribution of Disk Data files.  You can obtain better performance by placing data files, undo log files, and the data node file system on separate physical disks. If you do this with some or all of these sets of files, then you can (and should) set DiskIOThreadPool higher to enable separate threads to handle the files on each disk.

      In NDB 8.0.19 and later, you should also disable DiskDataUsingSameDisk when using a separate disk or disks for Disk Data files; this increases the rate at which checkpoints of Disk Data tablespaces can be performed.

    • Disk performance and types.  The number of threads that can be accommodated for Disk Data file handling is also dependent on the speed and throughput of the disks. Faster disks and higher throughput allow for more disk I/O threads. Our test results indicate that solid-state disk drives can handle many more disk I/O threads than conventional disks, and thus higher values for DiskIOThreadPool.

      Decreasing TimeBetweenGlobalCheckpoints is also recommended when using solid-state disk drives, in particular those using NVMe. See also Disk Data latency parameters.

    The default value for this parameter is 2.

  • Disk Data file system parameters.  The parameters in the following list make it possible to place NDB Cluster Disk Data files in specific directories without the need for using symbolic links.

    • FileSystemPathDD

      Version (or later) NDB 8.0.13
      Type or units filename
      Default FileSystemPath
      Range ...
      Restart Type IN

      If this parameter is specified, then NDB Cluster Disk Data data files and undo log files are placed in the indicated directory. This can be overridden for data files, undo log files, or both, by specifying values for FileSystemPathDataFiles, FileSystemPathUndoFiles, or both, as explained for these parameters. It can also be overridden for data files by specifying a path in the ADD DATAFILE clause of a CREATE TABLESPACE or ALTER TABLESPACE statement, and for undo log files by specifying a path in the ADD UNDOFILE clause of a CREATE LOGFILE GROUP or ALTER LOGFILE GROUP statement. If FileSystemPathDD is not specified, then FileSystemPath is used.

      If a FileSystemPathDD directory is specified for a given data node (including the case where the parameter is specified in the [ndbd default] section of the config.ini file), then starting that data node with --initial causes all files in the directory to be deleted.

    • FileSystemPathDataFiles

      Version (or later) NDB 8.0.13
      Type or units filename
      Default FileSystemPathDD
      Range ...
      Restart Type IN

      If this parameter is specified, then NDB Cluster Disk Data data files are placed in the indicated directory. This overrides any value set for FileSystemPathDD. This parameter can be overridden for a given data file by specifying a path in the ADD DATAFILE clause of a CREATE TABLESPACE or ALTER TABLESPACE statement used to create that data file. If FileSystemPathDataFiles is not specified, then FileSystemPathDD is used (or FileSystemPath, if FileSystemPathDD has also not been set).

      If a FileSystemPathDataFiles directory is specified for a given data node (including the case where the parameter is specified in the [ndbd default] section of the config.ini file), then starting that data node with --initial causes all files in the directory to be deleted.

    • FileSystemPathUndoFiles

      Version (or later) NDB 8.0.13
      Type or units filename
      Default FileSystemPathDD
      Range ...
      Restart Type IN

      If this parameter is specified, then NDB Cluster Disk Data undo log files are placed in the indicated directory. This overrides any value set for FileSystemPathDD. This parameter can be overridden for a given data file by specifying a path in the ADD UNDO clause of a CREATE LOGFILE GROUP or ALTER LOGFILE GROUP statement used to create that data file. If FileSystemPathUndoFiles is not specified, then FileSystemPathDD is used (or FileSystemPath, if FileSystemPathDD has also not been set).

      If a FileSystemPathUndoFiles directory is specified for a given data node (including the case where the parameter is specified in the [ndbd default] section of the config.ini file), then starting that data node with --initial causes all files in the directory to be deleted.

    For more information, see Section 23.5.10.1, “NDB Cluster Disk Data Objects”.

  • Disk Data object creation parameters.  The next two parameters enable you—when starting the cluster for the first time—to cause a Disk Data log file group, tablespace, or both, to be created without the use of SQL statements.

    • InitialLogFileGroup

      Version (or later) NDB 8.0.13
      Type or units string
      Default [see documentation]
      Range ...
      Restart Type S

      This parameter can be used to specify a log file group that is created when performing an initial start of the cluster. InitialLogFileGroup is specified as shown here:

      InitialLogFileGroup = [name=name;] [undo_buffer_size=size;] file-specification-list
      
      file-specification-list:
          file-specification[; file-specification[; ...]]
      
      file-specification:
          filename:size
      

      The name of the log file group is optional and defaults to DEFAULT-LG. The undo_buffer_size is also optional; if omitted, it defaults to 64M. Each file-specification corresponds to an undo log file, and at least one must be specified in the file-specification-list. Undo log files are placed according to any values that have been set for FileSystemPath, FileSystemPathDD, and FileSystemPathUndoFiles, just as if they had been created as the result of a CREATE LOGFILE GROUP or ALTER LOGFILE GROUP statement.

      Consider the following:

      InitialLogFileGroup = name=LG1; undo_buffer_size=128M; undo1.log:250M; undo2.log:150M
      

      This is equivalent to the following SQL statements:

      CREATE LOGFILE GROUP LG1
          ADD UNDOFILE 'undo1.log'
          INITIAL_SIZE 250M
          UNDO_BUFFER_SIZE 128M
          ENGINE NDBCLUSTER;
      
      ALTER LOGFILE GROUP LG1
          ADD UNDOFILE 'undo2.log'
          INITIAL_SIZE 150M
          ENGINE NDBCLUSTER;
      

      This logfile group is created when the data nodes are started with --initial.

      Resources for the initial log file group are added to the global memory pool along with those indicated by the value of SharedGlobalMemory.

      This parameter, if used, should always be set in the [ndbd default] section of the config.ini file. The behavior of an NDB Cluster when different values are set on different data nodes is not defined.

    • InitialTablespace

      Version (or later) NDB 8.0.13
      Type or units string
      Default [see documentation]
      Range ...
      Restart Type S

      This parameter can be used to specify an NDB Cluster Disk Data tablespace that is created when performing an initial start of the cluster. InitialTablespace is specified as shown here:

      InitialTablespace = [name=name;] [extent_size=size;] file-specification-list
      

      The name of the tablespace is optional and defaults to DEFAULT-TS. The extent_size is also optional; it defaults to 1M. The file-specification-list uses the same syntax as shown with the InitialLogfileGroup parameter, the only difference being that each file-specification used with InitialTablespace corresponds to a data file. At least one must be specified in the file-specification-list. Data files are placed according to any values that have been set for FileSystemPath, FileSystemPathDD, and FileSystemPathDataFiles, just as if they had been created as the result of a CREATE TABLESPACE or ALTER TABLESPACE statement.

      For example, consider the following line specifying InitialTablespace in the [ndbd default] section of the config.ini file (as with InitialLogfileGroup, this parameter should always be set in the [ndbd default] section, as the behavior of an NDB Cluster when different values are set on different data nodes is not defined):

      InitialTablespace = name=TS1; extent_size=8M; data1.dat:2G; data2.dat:4G
      

      This is equivalent to the following SQL statements:

      CREATE TABLESPACE TS1
          ADD DATAFILE 'data1.dat'
          EXTENT_SIZE 8M
          INITIAL_SIZE 2G
          ENGINE NDBCLUSTER;
      
      ALTER TABLESPACE TS1
          ADD DATAFILE 'data2.dat'
          INITIAL_SIZE 4G
          ENGINE NDBCLUSTER;
      

      This tablespace is created when the data nodes are started with --initial, and can be used whenever creating NDB Cluster Disk Data tables thereafter.

  • Disk Data latency parameters.  The two parameters listed here can be used to improve handling of latency issues with NDB Cluster Disk Data tables.

    • MaxDiskDataLatency

      Version (or later) NDB 8.0.19
      Type or units ms
      Default 0
      Range 0 - 8000
      Restart Type N
      Added NDB 8.0.19

      This parameter controls the maximum allowed mean latency for disk access (maximum 8000 milliseconds). When this limit is reached, NDB begins to abort transactions in order to decrease pressure on the Disk Data I/O subsystem. Use 0 to disable the latency check.

    • DiskDataUsingSameDisk

      Version (or later) NDB 8.0.19
      Type or units boolean
      Default true
      Range ...
      Restart Type N
      Added NDB 8.0.19

      Set this parameter to false if your Disk Data tablespaces use one or more separate disks. Doing so allows checkpoints to tablespaces to be executed at a higher rate than normally used for when disks are shared.

      When DiskDataUsingSameDisk is true, NDB decreases the rate of Disk Data checkpointing whenever an in-memory checkpoint is in progress to help ensure that disk load remains constant.

Disk Data and GCP Stop errors.  Errors encountered when using Disk Data tables such as Node nodeid killed this node because GCP stop was detected (error 2303) are often referred to as GCP stop errors. Such errors occur when the redo log is not flushed to disk quickly enough; this is usually due to slow disks and insufficient disk throughput.

You can help prevent these errors from occurring by using faster disks, and by placing Disk Data files on a separate disk from the data node file system. Reducing the value of TimeBetweenGlobalCheckpoints tends to decrease the amount of data to be written for each global checkpoint, and so may provide some protection against redo log buffer overflows when trying to write a global checkpoint; however, reducing this value also permits less time in which to write the GCP, so this must be done with caution.

In addition to the considerations given for DiskPageBufferMemory as explained previously, it is also very important that the DiskIOThreadPool configuration parameter be set correctly; having DiskIOThreadPool set too high is very likely to cause GCP stop errors (Bug #37227).

GCP stops can be caused by save or commit timeouts; the TimeBetweenEpochsTimeout data node configuration parameter determines the timeout for commits. However, it is possible to disable both types of timeouts by setting this parameter to 0.

Parameters for configuring send buffer memory allocation.  Send buffer memory is allocated dynamically from a memory pool shared between all transporters, which means that the size of the send buffer can be adjusted as necessary. (Previously, the NDB kernel used a fixed-size send buffer for every node in the cluster, which was allocated when the node started and could not be changed while the node was running.) The TotalSendBufferMemory and OverLoadLimit data node configuration parameters permit the setting of limits on this memory allocation. For more information about the use of these parameters (as well as SendBufferMemory), see Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”.

See also Section 23.5.7, “Adding NDB Cluster Data Nodes Online”.

Redo log over-commit handling.  It is possible to control a data node's handling of operations when too much time is taken flushing redo logs to disk. This occurs when a given redo log flush takes longer than RedoOverCommitLimit seconds, more than RedoOverCommitCounter times, causing any pending transactions to be aborted. When this happens, the API node that sent the transaction can handle the operations that should have been committed either by queuing the operations and re-trying them, or by aborting them, as determined by DefaultOperationRedoProblemAction. The data node configuration parameters for setting the timeout and number of times it may be exceeded before the API node takes this action are described in the following list:

  • RedoOverCommitCounter

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default 3
    Range 1 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units numeric
    Default 3
    Range 1 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When RedoOverCommitLimit is exceeded when trying to write a given redo log to disk this many times or more, any transactions that were not committed as a result are aborted, and an API node where any of these transactions originated handles the operations making up those transactions according to its value for DefaultOperationRedoProblemAction (by either queuing the operations to be re-tried, or aborting them).

  • RedoOverCommitLimit

    Version (or later) NDB 8.0.13
    Type or units seconds
    Default 20
    Range 1 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Version (or later) NDB 8.0.19
    Type or units seconds
    Default 20
    Range 1 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter sets an upper limit in seconds for trying to write a given redo log to disk before timing out. The number of times the data node tries to flush this redo log, but takes longer than RedoOverCommitLimit, is kept and compared with RedoOverCommitCounter, and when flushing takes too long more times than the value of that parameter, any transactions that were not committed as a result of the flush timeout are aborted. When this occurs, the API node where any of these transactions originated handles the operations making up those transactions according to its DefaultOperationRedoProblemAction setting (it either queues the operations to be re-tried, or aborts them).

Controlling restart attempts.  It is possible to exercise finely-grained control over restart attempts by data nodes when they fail to start using the MaxStartFailRetries and StartFailRetryDelay data node configuration parameters.

MaxStartFailRetries limits the total number of retries made before giving up on starting the data node, StartFailRetryDelay sets the number of seconds between retry attempts. These parameters are listed here:

  • StartFailRetryDelay

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Use this parameter to set the number of seconds between restart attempts by the data node in the event on failure on startup. The default is 0 (no delay).

    Both this parameter and MaxStartFailRetries are ignored unless StopOnError is equal to 0.

  • MaxStartFailRetries

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 3
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Use this parameter to limit the number restart attempts made by the data node in the event that it fails on startup. The default is 3 attempts.

    Both this parameter and StartFailRetryDelay are ignored unless StopOnError is equal to 0.

NDB index statistics parameters.  The parameters in the following list relate to NDB index statistics generation.

  • IndexStatAutoCreate

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0, 1
    Restart Type S

    Enable (set equal to 1) or disable (set equal to 0) automatic statistics collection when indexes are created. Disabled by default.

  • IndexStatAutoUpdate

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0, 1
    Restart Type S

    Enable (set equal to 1) or disable (set equal to 0) monitoring of indexes for changes and trigger automatic statistics updates these are detected. The amount and degree of change needed to trigger the updates are determined by the settings for the IndexStatTriggerPct and IndexStatTriggerScale options.

  • IndexStatSaveSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 32768
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    Maximum space in bytes allowed for the saved statistics of any given index in the NDB system tables and in the mysqld memory cache.

    At least one sample is always produced, regardless of any size limit. This size is scaled by IndexStatSaveScale.

    The size specified by IndexStatSaveSize is scaled by the value of IndexStatTriggerPct for a large index, times 0.01. This is further multiplied by the logarithm to the base 2 of the index size. Setting IndexStatTriggerPct equal to 0 disables the scaling effect.

  • IndexStatSaveScale

    Version (or later) NDB 8.0.13
    Type or units percentage
    Default 100
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    The size specified by IndexStatSaveSize is scaled by the value of IndexStatTriggerPct for a large index, times 0.01. This is further multiplied by the logarithm to the base 2 of the index size. Setting IndexStatTriggerPct equal to 0 disables the scaling effect.

  • IndexStatTriggerPct

    Version (or later) NDB 8.0.13
    Type or units percentage
    Default 100
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    Percentage change in updates that triggers an index statistics update. The value is scaled by IndexStatTriggerScale. You can disable this trigger altogether by setting IndexStatTriggerPct to 0.

  • IndexStatTriggerScale

    Version (or later) NDB 8.0.13
    Type or units percentage
    Default 100
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    Scale IndexStatTriggerPct by this amount times 0.01 for a large index. A value of 0 disables scaling.

  • IndexStatUpdateDelay

    Version (or later) NDB 8.0.13
    Type or units seconds
    Default 60
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type IN

    Minimum delay in seconds between automatic index statistics updates for a given index. Setting this variable to 0 disables any delay. The default is 60 seconds.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.16 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.7 Defining SQL and Other API Nodes in an NDB Cluster

The [mysqld] and [api] sections in the config.ini file define the behavior of the MySQL servers (SQL nodes) and other applications (API nodes) used to access cluster data. None of the parameters shown is required. If no computer or host name is provided, any host can use this SQL or API node.

Generally speaking, a [mysqld] section is used to indicate a MySQL server providing an SQL interface to the cluster, and an [api] section is used for applications other than mysqld processes accessing cluster data, but the two designations are actually synonymous; you can, for instance, list parameters for a MySQL server acting as an SQL node in an [api] section.

Note

For a discussion of MySQL server options for NDB Cluster, see Section 23.3.3.9.1, “MySQL Server Options for NDB Cluster”. For information about MySQL server system variables relating to NDB Cluster, see Section 23.3.3.9.2, “NDB Cluster System Variables”.

  • Id

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 255
    Restart Type IS

    The Id is an integer value used to identify the node in all cluster internal messages. The permitted range of values is 1 to 255 inclusive. This value must be unique for each node in the cluster, regardless of the type of node.

    Note

    In NDB 8.0.18 and later, data node IDs must be less than 145. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for API nodes (and management nodes) to values greater than 144. (Previous to NDB 8.0.18, the maximum supported value for a data node ID was 48.)

    NodeId is the preferred parameter name to use when identifying API nodes. (Id continues to be supported for backward compatibility, but is now deprecated and generates a warning when used. It is also subject to future removal.)

  • ConnectionMap

    Version (or later) NDB 8.0.13
    Type or units string
    Default [none]
    Range ...
    Restart Type N

    Specifies which data nodes to connect.

  • NodeId

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 1 - 255
    Restart Type IS

    The NodeId is an integer value used to identify the node in all cluster internal messages. The permitted range of values is 1 to 255 inclusive. This value must be unique for each node in the cluster, regardless of the type of node.

    Note

    In NDB 8.0.18 and later, data node IDs must be less than 145. If you plan to deploy a large number of data nodes, it is a good idea to limit the node IDs for API nodes (and management nodes) to values greater than 144. (Previous to NDB 8.0.18, the maximum supported value for a data node ID was 48.)

    NodeId is the preferred parameter name to use when identifying management nodes. An alias, Id, was used for this purpose in very old versions of NDB Cluster, and continues to be supported for backward compatibility; it is now deprecated and generates a warning when used, and is subject to removal in a future release of NDB Cluster.

  • ExecuteOnComputer

    Version (or later) NDB 8.0.13
    Type or units name
    Default [none]
    Range ...
    Restart Type S
    Deprecated Yes (in NDB 7.5)

    This refers to the Id set for one of the computers (hosts) defined in a [computer] section of the configuration file.

    Important

    This parameter is deprecated, and is subject to removal in a future release. Use the HostName parameter instead.

  • The node ID for this node can be given out only to connections that explicitly request it. A management server that requests any node ID cannot use this one. This parameter can be used when running multiple management servers on the same host, and HostName is not sufficient for distinguishing among processes. Intended for use in testing.

  • HostName

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    Specifying this parameter defines the hostname of the computer on which the SQL node (API node) is to reside. To specify a hostname, either this parameter or ExecuteOnComputer is required.

    If no HostName or ExecuteOnComputer is specified in a given [mysql] or [api] section of the config.ini file, then an SQL or API node may connect using the corresponding slot from any host which can establish a network connection to the management server host machine. This differs from the default behavior for data nodes, where localhost is assumed for HostName unless otherwise specified.

  • LocationDomainId

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 16
    Restart Type S

    Assigns an SQL or other API node to a specific availability domain (also known as an availability zone) within a cloud. By informing NDB which nodes are in which availability domains, performance can be improved in a cloud environment in the following ways:

    • If requested data is not found on the same node, reads can be directed to another node in the same availability domain.

    • Communication between nodes in different availability domains are guaranteed to use NDB transporters' WAN support without any further manual intervention.

    • The transporter's group number can be based on which availability domain is used, such that also SQL and other API nodes communicate with local data nodes in the same availability domain whenever possible.

    • The arbitrator can be selected from an availability domain in which no data nodes are present, or, if no such availability domain can be found, from a third availability domain.

    LocationDomainId takes an integer value between 0 and 16 inclusive, with 0 being the default; using 0 is the same as leaving the parameter unset.

  • ArbitrationRank

    Version (or later) NDB 8.0.13
    Type or units 0-2
    Default 0
    Range 0 - 2
    Restart Type N

    This parameter defines which nodes can act as arbitrators. Both management nodes and SQL nodes can be arbitrators. A value of 0 means that the given node is never used as an arbitrator, a value of 1 gives the node high priority as an arbitrator, and a value of 2 gives it low priority. A normal configuration uses the management server as arbitrator, setting its ArbitrationRank to 1 (the default for management nodes) and those for all SQL nodes to 0 (the default for SQL nodes).

    By setting ArbitrationRank to 0 on all management and SQL nodes, you can disable arbitration completely. You can also control arbitration by overriding this parameter; to do so, set the Arbitration parameter in the [ndbd default] section of the config.ini global configuration file.

  • ArbitrationDelay

    Version (or later) NDB 8.0.13
    Type or units milliseconds
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Setting this parameter to any other value than 0 (the default) means that responses by the arbitrator to arbitration requests are delayed by the stated number of milliseconds. It is usually not necessary to change this value.

  • BatchByteSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 16K
    Range 1K - 1M
    Restart Type N

    For queries that are translated into full table scans or range scans on indexes, it is important for best performance to fetch records in properly sized batches. It is possible to set the proper size both in terms of number of records (BatchSize) and in terms of bytes (BatchByteSize). The actual batch size is limited by both parameters.

    The speed at which queries are performed can vary by more than 40% depending upon how this parameter is set.

    This parameter is measured in bytes. The default value is 16K.

  • BatchSize

    Version (or later) NDB 8.0.13
    Type or units records
    Default 256
    Range 1 - 992
    Restart Type N

    This parameter is measured in number of records and is by default set to 256. The maximum size is 992.

  • ExtraSendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter specifies the amount of transporter send buffer memory to allocate in addition to any that has been set using TotalSendBufferMemory, SendBufferMemory, or both.

  • HeartbeatThreadPriority

    Version (or later) NDB 8.0.13
    Type or units string
    Default [none]
    Range ...
    Restart Type S

    Use this parameter to set the scheduling policy and priority of heartbeat threads for management and API nodes. The syntax for setting this parameter is shown here:

    HeartbeatThreadPriority = policy[, priority]
    
    policy:
      {FIFO | RR}
    

    When setting this parameter, you must specify a policy. This is one of FIFO (first in, first in) or RR (round robin). This followed optionally by the priority (an integer).

  • MaxScanBatchSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 256K
    Range 32K - 16M
    Restart Type N

    The batch size is the size of each batch sent from each data node. Most scans are performed in parallel to protect the MySQL Server from receiving too much data from many nodes in parallel; this parameter sets a limit to the total batch size over all nodes.

    The default value of this parameter is set to 256KB. Its maximum size is 16MB.

  • TotalSendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 256K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    This parameter is used to determine the total amount of memory to allocate on this node for shared send buffer memory among all configured transporters.

    If this parameter is set, its minimum permitted value is 256KB; 0 indicates that the parameter has not been set. For more detailed information, see Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”.

  • AutoReconnect

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    This parameter is false by default. This forces disconnected API nodes (including MySQL Servers acting as SQL nodes) to use a new connection to the cluster rather than attempting to re-use an existing one, as re-use of connections can cause problems when using dynamically-allocated node IDs. (Bug #45921)

    Note

    This parameter can be overridden using the NDB API. For more information, see Ndb_cluster_connection::set_auto_reconnect(), and Ndb_cluster_connection::get_auto_reconnect().

  • DefaultOperationRedoProblemAction

    Version (or later) NDB 8.0.13
    Type or units enumeration
    Default QUEUE
    Range ABORT, QUEUE
    Restart Type S

    This parameter (along with RedoOverCommitLimit and RedoOverCommitCounter) controls the data node's handling of operations when too much time is taken flushing redo logs to disk. This occurs when a given redo log flush takes longer than RedoOverCommitLimit seconds, more than RedoOverCommitCounter times, causing any pending transactions to be aborted.

    When this happens, the node can respond in either of two ways, according to the value of DefaultOperationRedoProblemAction, listed here:

    • ABORT: Any pending operations from aborted transactions are also aborted.

    • QUEUE: Pending operations from transactions that were aborted are queued up to be re-tried. This the default. Pending operations are still aborted when the redo log runs out of space—that is, when P_TAIL_PROBLEM errors occur.

  • DefaultHashMapSize

    Version (or later) NDB 8.0.13
    Type or units buckets
    Default 3840
    Range 0 - 3840
    Restart Type N

    The size of the table hash maps used by NDB is configurable using this parameter. DefaultHashMapSize can take any of three possible values (0, 240, 3840). These values and their effects are described in the following table.

    Table 23.17 DefaultHashMapSize parameter values

    Value Description / Effect
    0 Use the lowest value set, if any, for this parameter among all data nodes and API nodes in the cluster; if it is not set on any data or API node, use the default value.
    240 Old default hash map size
    3840 Hash map size used by default in NDB 8.0

    The original intended use for this parameter was to facilitate upgrades and downgrades to and from older NDB Cluster versions, in which the hash map size differed, due to the fact that this change was not otherwise backward compatible. This is not an issue when upgrading to or downgrading from NDB Cluster 8.0.

  • Wan

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    Use WAN TCP setting as default.

  • ConnectBackoffMaxTime

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    In an NDB Cluster with many unstarted data nodes, the value of this parameter can be raised to circumvent connection attempts to data nodes which have not yet begun to function in the cluster, as well as moderate high traffic to management nodes. As long as the API node is not connected to any new data nodes, the value of the StartConnectBackoffMaxTime parameter is applied; otherwise, ConnectBackoffMaxTime is used to determine the length of time in milliseconds to wait between connection attempts.

    Time elapsed during node connection attempts is not taken into account when calculating elapsed time for this parameter. The timeout is applied with approximately 100 ms resolution, starting with a 100 ms delay; for each subsequent attempt, the length of this period is doubled until it reaches ConnectBackoffMaxTime milliseconds, up to a maximum of 100000 ms (100s).

    Once the API node is connected to a data node and that node reports (in a heartbeat message) that it has connected to other data nodes, connection attempts to those data nodes are no longer affected by this parameter, and are made every 100 ms thereafter until connected. Once a data node has started, it can take up HeartbeatIntervalDbApi for the API node to be notified that this has occurred.

  • StartConnectBackoffMaxTime

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    In an NDB Cluster with many unstarted data nodes, the value of this parameter can be raised to circumvent connection attempts to data nodes which have not yet begun to function in the cluster, as well as moderate high traffic to management nodes. As long as the API node is not connected to any new data nodes, the value of the StartConnectBackoffMaxTime parameter is applied; otherwise, ConnectBackoffMaxTime is used to determine the length of time in milliseconds to wait between connection attempts.

    Time elapsed during node connection attempts is not taken into account when calculating elapsed time for this parameter. The timeout is applied with approximately 100 ms resolution, starting with a 100 ms delay; for each subsequent attempt, the length of this period is doubled until it reaches StartConnectBackoffMaxTime milliseconds, up to a maximum of 100000 ms (100s).

    Once the API node is connected to a data node and that node reports (in a heartbeat message) that it has connected to other data nodes, connection attempts to those data nodes are no longer affected by this parameter, and are made every 100 ms thereafter until connected. Once a data node has started, it can take up HeartbeatIntervalDbApi for the API node to be notified that this has occurred.

API Node Debugging Parameters.  You can use the ApiVerbose configuration parameter to enable debugging output from a given API node. This parameter takes an integer value. 0 is the default, and disables such debugging; 1 enables debugging output to the cluster log; 2 adds DBDICT debugging output as well. (Bug #20638450) See also DUMP 1229.

You can also obtain information from a MySQL server running as an NDB Cluster SQL node using SHOW STATUS in the mysql client, as shown here:

mysql> SHOW STATUS LIKE 'ndb%';
+-----------------------------+----------------+
| Variable_name               | Value          |
+-----------------------------+----------------+
| Ndb_cluster_node_id         | 5              |
| Ndb_config_from_host        | 198.51.100.112 |
| Ndb_config_from_port        | 1186           |
| Ndb_number_of_storage_nodes | 4              |
+-----------------------------+----------------+
4 rows in set (0.02 sec)

For information about the status variables appearing in the output from this statement, see Section 23.3.3.9.3, “NDB Cluster Status Variables”.

Note

To add new SQL or API nodes to the configuration of a running NDB Cluster, it is necessary to perform a rolling restart of all cluster nodes after adding new [mysqld] or [api] sections to the config.ini file (or files, if you are using more than one management server). This must be done before the new SQL or API nodes can connect to the cluster.

It is not necessary to perform any restart of the cluster if new SQL or API nodes can employ previously unused API slots in the cluster configuration to connect to the cluster.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.18 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.8 Defining the System

The [system] section is used for parameters applying to the cluster as a whole. The Name system parameter is used with MySQL Enterprise Monitor; ConfigGenerationNumber and PrimaryMGMNode are not used in production environments. Except when using NDB Cluster with MySQL Enterprise Monitor, is not necessary to have a [system] section in the config.ini file.

More information about these parameters can be found in the following list:

  • ConfigGenerationNumber

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Configuration generation number. This parameter is currently unused.

  • Name

    Version (or later) NDB 8.0.13
    Type or units string
    Default [none]
    Range ...
    Restart Type N

    Set a name for the cluster. This parameter is required for deployments with MySQL Enterprise Monitor; it is otherwise unused.

    You can obtain the value of this parameter by checking the Ndb_system_name status variable. In NDB API applications, you can also retrieve it using get_system_name().

  • PrimaryMGMNode

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Node ID of the primary management node. This parameter is currently unused.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.19 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.9 MySQL Server Options and Variables for NDB Cluster

This section provides information about MySQL server options, server and status variables that are specific to NDB Cluster. For general information on using these, and for other options and variables not specific to NDB Cluster, see Section 5.1, “The MySQL Server”.

For NDB Cluster configuration parameters used in the cluster configuration file (usually named config.ini), see Section 23.3, “Configuration of NDB Cluster”.

23.3.3.9.1 MySQL Server Options for NDB Cluster

This section provides descriptions of mysqld server options relating to NDB Cluster. For information about mysqld options not specific to NDB Cluster, and for general information about the use of options with mysqld, see Section 5.1.7, “Server Command Options”.

For information about command-line options used with other NDB Cluster processes (ndbd, ndb_mgmd, and ndb_mgm), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”. For information about command-line options used with NDB utility programs (such as ndb_desc, ndb_size.pl, and ndb_show_tables), see Section 23.4, “NDB Cluster Programs”.

  • --ndbcluster

    Command-Line Format --ndbcluster[=value]
    Disabled by skip-ndbcluster
    Type Enumeration
    Default Value ON
    Valid Values

    OFF

    FORCE

    The NDBCLUSTER storage engine is necessary for using NDB Cluster. If a mysqld binary includes support for the NDBCLUSTER storage engine, the engine is disabled by default. Use the --ndbcluster option to enable it. Use --skip-ndbcluster to explicitly disable the engine.

    The --ndbcluster option is ignored (and the NDB storage engine is not enabled) if --initialize is also used. (It is neither necessary nor desirable to use this option together with --initialize.)

  • --ndb-allow-copying-alter-table=[ON|OFF]

    Command-Line Format --ndb-allow-copying-alter-table[={OFF|ON}]
    System Variable ndb_allow_copying_alter_table
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    Let ALTER TABLE and other DDL statements use copying operations on NDB tables. Set to OFF to keep this from happening; doing so may improve performance of critical applications.

  • --ndb-batch-size=#

    Command-Line Format --ndb-batch-size
    System Variable ndb_batch_size
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 32768
    Minimum Value 0
    Maximum Value 31536000

    This sets the size in bytes that is used for NDB transaction batches.

  • --ndb-cluster-connection-pool=#

    Command-Line Format --ndb-cluster-connection-pool
    System Variable ndb_cluster_connection_pool
    System Variable ndb_cluster_connection_pool
    Scope Global
    Scope Global
    Dynamic No
    Dynamic No
    SET_VAR Hint Applies No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 63

    By setting this option to a value greater than 1 (the default), a mysqld process can use multiple connections to the cluster, effectively mimicking several SQL nodes. Each connection requires its own [api] or [mysqld] section in the cluster configuration (config.ini) file, and counts against the maximum number of API connections supported by the cluster.

    Suppose that you have 2 cluster host computers, each running an SQL node whose mysqld process was started with --ndb-cluster-connection-pool=4; this means that the cluster must have 8 API slots available for these connections (instead of 2). All of these connections are set up when the SQL node connects to the cluster, and are allocated to threads in a round-robin fashion.

    This option is useful only when running mysqld on host machines having multiple CPUs, multiple cores, or both. For best results, the value should be smaller than the total number of cores available on the host machine. Setting it to a value greater than this is likely to degrade performance severely.

    Important

    Because each SQL node using connection pooling occupies multiple API node slots—each slot having its own node ID in the cluster—you must not use a node ID as part of the cluster connection string when starting any mysqld process that employs connection pooling.

    Setting a node ID in the connection string when using the --ndb-cluster-connection-pool option causes node ID allocation errors when the SQL node attempts to connect to the cluster.

  • --ndb-cluster-connection-pool-nodeids=list

    Command-Line Format --ndb-cluster-connection-pool-nodeids
    System Variable ndb_cluster_connection_pool_nodeids
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Set
    Default Value

    Specifies a comma-separated list of node IDs for connections to the cluster used by an SQL node. The number of nodes in this list must be the same as the value set for the --ndb-cluster-connection-pool option.

  • --ndb-blob-read-batch-bytes=bytes

    Command-Line Format --ndb-blob-read-batch-bytes
    System Variable ndb_blob_read_batch_bytes
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 65536
    Minimum Value 0
    Maximum Value 4294967295

    This option can be used to set the size (in bytes) for batching of BLOB data reads in NDB Cluster applications. When this batch size is exceeded by the amount of BLOB data to be read within the current transaction, any pending BLOB read operations are immediately executed.

    The maximum value for this option is 4294967295; the default is 65536. Setting it to 0 has the effect of disabling BLOB read batching.

    Note

    In NDB API applications, you can control BLOB write batching with the setMaxPendingBlobReadBytes() and getMaxPendingBlobReadBytes() methods.

  • --ndb-blob-write-batch-bytes=bytes

    Command-Line Format --ndb-blob-write-batch-bytes
    System Variable ndb_blob_write_batch_bytes
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 65536
    Minimum Value 0
    Maximum Value 4294967295

    This option can be used to set the size (in bytes) for batching of BLOB data writes in NDB Cluster applications. When this batch size is exceeded by the amount of BLOB data to be written within the current transaction, any pending BLOB write operations are immediately executed.

    The maximum value for this option is 4294967295; the default is 65536. Setting it to 0 has the effect of disabling BLOB write batching.

    Note

    In NDB API applications, you can control BLOB write batching with the setMaxPendingBlobWriteBytes() and getMaxPendingBlobWriteBytes() methods.

  • --ndb-connectstring=connection_string

    Command-Line Format --ndb-connectstring
    Type String

    When using the NDBCLUSTER storage engine, this option specifies the management server that distributes cluster configuration data. See Section 23.3.3.3, “NDB Cluster Connection Strings”, for syntax.

  • --ndb-default-column-format=[FIXED|DYNAMIC]

    Command-Line Format --ndb-default-column-format={FIXED|DYNAMIC}
    System Variable ndb_default_column_format
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value FIXED
    Valid Values

    FIXED

    DYNAMIC

    Sets the default COLUMN_FORMAT and ROW_FORMAT for new tables (see Section 13.1.20, “CREATE TABLE Statement”). The default is FIXED.

  • --ndb-deferred-constraints=[0|1]

    Command-Line Format --ndb-deferred-constraints
    System Variable ndb_deferred_constraints
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    Controls whether or not constraint checks on unique indexes are deferred until commit time, where such checks are supported. 0 is the default.

    This option is not normally needed for operation of NDB Cluster or NDB Cluster Replication, and is intended primarily for use in testing.

  • --ndb-schema-dist-timeout=#

    Command-Line Format --ndb-schema-dist-timeout=#
    Introduced 8.0.17-ndb-8.0.17
    System Variable ndb_schema_dist_timeout
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 120
    Minimum Value 5
    Maximum Value 1200
    Unit seconds

    Specifies the maximum time in seconds that this mysqld waits for a schema operation to complete before marking it as having timed out.

  • --ndb-distribution=[KEYHASH|LINHASH]

    Command-Line Format --ndb-distribution={KEYHASH|LINHASH}
    System Variable ndb_distribution
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value KEYHASH
    Valid Values

    LINHASH

    KEYHASH

    Controls the default distribution method for NDB tables. Can be set to either of KEYHASH (key hashing) or LINHASH (linear hashing). KEYHASH is the default.

  • --ndb-log-apply-status

    Command-Line Format --ndb-log-apply-status[={OFF|ON}]
    System Variable ndb_log_apply_status
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Causes a replica mysqld to log any updates received from its immediate source to the mysql.ndb_apply_status table in its own binary log using its own server ID rather than the server ID of the source. In a circular or chain replication setting, this allows such updates to propagate to the mysql.ndb_apply_status tables of any MySQL servers configured as replicas of the current mysqld.

    In a chain replication setup, using this option allows downstream (replica) clusters to be aware of their positions relative to all of their upstream contributors (sourcess).

    In a circular replication setup, this option causes changes to ndb_apply_status tables to complete the entire circuit, eventually propagating back to the originating NDB Cluster. This also allows a cluster acting as a replication source to see when its changes (epochs) have been applied to the other clusters in the circle.

    This option has no effect unless the MySQL server is started with the --ndbcluster option.

  • --ndb-log-empty-epochs=[ON|OFF]

    Command-Line Format --ndb-log-empty-epochs[={OFF|ON}]
    System Variable ndb_log_empty_epochs
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Causes epochs during which there were no changes to be written to the ndb_apply_status and ndb_binlog_index tables, even when log_slave_updates is enabled.

    By default this option is disabled. Disabling --ndb-log-empty-epochs causes epoch transactions with no changes not to be written to the binary log, although a row is still written even for an empty epoch in ndb_binlog_index.

    Because --ndb-log-empty-epochs=1 causes the size of the ndb_binlog_index table to increase independently of the size of the binary log, users should be prepared to manage the growth of this table, even if they expect the cluster to be idle a large part of the time.

  • --ndb-log-empty-update=[ON|OFF]

    Command-Line Format --ndb-log-empty-update[={OFF|ON}]
    System Variable ndb_log_empty_update
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Causes updates that produced no changes to be written to the ndb_apply_status and ndb_binlog_index tables, when when log_slave_updates is enabled.

    By default this option is disabled (OFF). Disabling --ndb-log-empty-update causes updates with no changes not to be written to the binary log.

  • --ndb-log-exclusive-reads=[0|1]

    Command-Line Format --ndb-log-exclusive-reads[={OFF|ON}]
    System Variable ndb_log_exclusive_reads
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value 0

    Starting the server with this option causes primary key reads to be logged with exclusive locks, which allows for NDB Cluster Replication conflict detection and resolution based on read conflicts. You can also enable and disable these locks at runtime by setting the value of the ndb_log_exclusive_reads system variable to 1 or 0, respectively. 0 (disable locking) is the default.

    For more information, see Read conflict detection and resolution.

  • --ndb-log-fail-terminate

    Command-Line Format --ndb-log-fail-terminate
    Introduced 8.0.21-ndb-8.0.21
    System Variable ndb_log_fail_terminate
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value FALSE

    When this option is specified, and complete logging of all found row events is not possible, the mysqld process is terminated.

  • --ndb-log-orig

    Command-Line Format --ndb-log-orig[={OFF|ON}]
    System Variable ndb_log_orig
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Log the originating server ID and epoch in the ndb_binlog_index table.

    Note

    This makes it possible for a given epoch to have multiple rows in ndb_binlog_index, one for each originating epoch.

    For more information, see Section 23.6.4, “NDB Cluster Replication Schema and Tables”.

  • --ndb-log-transaction-id

    Command-Line Format --ndb-log-transaction-id[={OFF|ON}]
    System Variable ndb_log_transaction_id
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Causes a replica mysqld to write the NDB transaction ID in each row of the binary log. The default value is FALSE.

    This option is not supported in mainline MySQL Server 8.0. It is required to enable NDB Cluster Replication conflict detection and resolution using the NDB$EPOCH_TRANS() function (see NDB$EPOCH_TRANS()). For more information, see Section 23.6.11, “NDB Cluster Replication Conflict Resolution”.

    The deprecated log_bin_use_v1_row_events system variable, which defaults to OFF, must not be set to ON when you use --ndb-log-transaction-id.

  • --ndb-log-update-minimal

    Command-Line Format --ndb-log-update-minimal[={OFF|ON}]
    System Variable ndb_log_update_minimal
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Log updates in a minimal fashion, by writing only the primary key values in the before image, and only the changed columns in the after image. This may cause compatibility problems if replicating to storage engines other than NDB.

  • --ndb-mgmd-host=host[:port]

    Command-Line Format --ndb-mgmd-host=host_name[:port_num]
    Type String
    Default Value localhost:1186

    Can be used to set the host and port number of a single management server for the program to connect to. If the program requires node IDs or references to multiple management servers (or both) in its connection information, use the --ndb-connectstring option instead.

  • --ndb-nodeid=#

    Command-Line Format --ndb-nodeid=#
    Status Variable Ndb_cluster_node_id
    Scope Global
    Dynamic No
    Type Integer
    Minimum Value 1
    Maximum Value 255
    Maximum Value 63

    Set this MySQL server's node ID in an NDB Cluster.

    The --ndb-nodeid option overrides any node ID set with --ndb-connectstring, regardless of the order in which the two options are used.

    In addition, if --ndb-nodeid is used, then either a matching node ID must be found in a [mysqld] or [api] section of config.ini, or there must be an open [mysqld] or [api] section in the file (that is, a section without a NodeId or Id parameter specified). This is also true if the node ID is specified as part of the connection string.

    Regardless of how the node ID is determined, its is shown as the value of the global status variable Ndb_cluster_node_id in the output of SHOW STATUS, and as cluster_node_id in the connection row of the output of SHOW ENGINE NDBCLUSTER STATUS.

    For more information about node IDs for NDB Cluster SQL nodes, see Section 23.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”.

  • --ndbinfo={ON|OFF|FORCE}

    Command-Line Format --ndbinfo[=value] (≥ 8.0.13-ndb-8.0.13)
    Introduced 8.0.13-ndb-8.0.13
    Type Enumeration
    Default Value ON
    Valid Values

    ON

    OFF

    FORCE

    Enables the plugin for the ndbinfo information database. By default this is ON whenever NDBCLUSTER is enabled.

  • --ndb-optimization-delay=milliseconds

    Command-Line Format --ndb-optimization-delay=#
    System Variable ndb_optimization_delay
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 10
    Minimum Value 0
    Maximum Value 100000

    Set the number of milliseconds to wait between sets of rows by OPTIMIZE TABLE statements on NDB tables. The default is 10.

  • --ndb-transid-mysql-connection-map=state

    Command-Line Format --ndb-transid-mysql-connection-map[=state]
    Type Enumeration
    Default Value ON
    Valid Values

    ON

    OFF

    FORCE

    Enables or disables the plugin that handles the ndb_transid_mysql_connection_map table in the INFORMATION_SCHEMA database. Takes one of the values ON, OFF, or FORCE. ON (the default) enables the plugin. OFF disables the plugin, which makes ndb_transid_mysql_connection_map inaccessible. FORCE keeps the MySQL Server from starting if the plugin fails to load and start.

    You can see whether the ndb_transid_mysql_connection_map table plugin is running by checking the output of SHOW PLUGINS.

  • --ndb-wait-connected=seconds

    Command-Line Format --ndb-wait-connected=#
    System Variable ndb_wait_connected
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 30
    Minimum Value 0
    Maximum Value 31536000

    This option sets the period of time that the MySQL server waits for connections to NDB Cluster management and data nodes to be established before accepting MySQL client connections. The time is specified in seconds. The default value is 30.

  • --ndb-wait-setup=seconds

    Command-Line Format --ndb-wait-setup=#
    System Variable ndb_wait_setup
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 30
    Default Value 30
    Default Value 15
    Default Value 15
    Minimum Value 0
    Maximum Value 31536000

    This variable shows the period of time that the MySQL server waits for the NDB storage engine to complete setup before timing out and treating NDB as unavailable. The time is specified in seconds. The default value is 30.

  • --skip-ndbcluster

    Command-Line Format --skip-ndbcluster

    Disable the NDBCLUSTER storage engine. This is the default for binaries that were built with NDBCLUSTER storage engine support; the server allocates memory and other resources for this storage engine only if the --ndbcluster option is given explicitly. See Section 23.3.1, “Quick Test Setup of NDB Cluster”, for an example.

23.3.3.9.2 NDB Cluster System Variables

This section provides detailed information about MySQL server system variables that are specific to NDB Cluster and the NDB storage engine. For system variables not specific to NDB Cluster, see Section 5.1.8, “Server System Variables”. For general information on using system variables, see Section 5.1.9, “Using System Variables”.

  • ndb_autoincrement_prefetch_sz

    Command-Line Format --ndb-autoincrement-prefetch-sz=#
    System Variable ndb_autoincrement_prefetch_sz
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value (≥ 8.0.19-ndb-8.0.19) 512
    Default Value (≤ 8.0.18-ndb-8.0.18) 1
    Minimum Value 1
    Maximum Value 65536

    Determines the probability of gaps in an autoincremented column. Set it to 1 to minimize this. Setting it to a high value for optimization makes inserts faster, but decreases the likelihood of consecutive autoincrement numbers being used in a batch of inserts.

    This variable affects only the number of AUTO_INCREMENT IDs that are fetched between statements; within a given statement, at least 32 IDs are obtained at a time.

    Important

    This variable does not affect inserts performed using INSERT ... SELECT.

  • ndb_cache_check_time

    Command-Line Format --ndb-cache-check-time=#
    Deprecated Yes
    System Variable ndb_cache_check_time
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0

    The number of milliseconds that elapse between checks of NDB Cluster SQL nodes by the MySQL query cache. Setting this to 0 (the default and minimum value) means that the query cache checks for validation on every query.

    The recommended maximum value for this variable is 1000, which means that the check is performed once per second. A larger value means that the check is performed and possibly invalidated due to updates on different SQL nodes less often. It is generally not desirable to set this to a value greater than 2000.

    Note

    The query cache ndb_cache_check_time are deprecated in MySQL 5.7; the query cache was removed in MySQL 8.0.

  • ndb_clear_apply_status

    Command-Line Format --ndb-clear-apply-status[={OFF|ON}]
    System Variable ndb_clear_apply_status
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    By the default, executing RESET SLAVE causes an NDB Cluster replica to purge all rows from its ndb_apply_status table. You can disable this by setting ndb_clear_apply_status=OFF.

  • ndb_conflict_role

    Command-Line Format --ndb-conflict-role=value
    Introduced 8.0.23-ndb-8.0.23
    System Variable ndb_conflict_role
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value NONE
    Valid Values

    NONE

    PRIMARY

    SECONDARY

    PASS

    Determines the role of this SQL node (and NDB Cluster) in a circular (active-active) replication setup. ndb_slave_conflict_role can take any one of the values PRIMARY, SECONDARY, PASS, or NULL (the default). The replica SQL thread must be stopped before you can change ndb_slave_conflict_role. In addition, it is not possible to change directly between PASS and either of PRIMARY or SECONDARY directly; in such cases, you must ensure that the SQL thread is stopped, then execute SET @@GLOBAL.ndb_slave_conflict_role = 'NONE' first.

    This variable replaces ndb_slave_conflict_role, which is deprecated as of NDB 8.0.23.

    For more information, see Section 23.6.11, “NDB Cluster Replication Conflict Resolution”.

  • ndb_data_node_neighbour

    Command-Line Format --ndb-data-node-neighbour=#
    System Variable ndb_data_node_neighbour
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 255

    Sets the ID of a nearest data node—that is, a preferred nonlocal data node is chosen to execute the transaction, rather than one running on the same host as the SQL or API node. This used to ensure that when a fully replicated table is accessed, we access it on this data node, to ensure that the local copy of the table is always used whenever possible. This can also be used for providing hints for transactions.

    This can improve data access times in the case of a node that is physically closer than and thus has higher network throughput than others on the same host.

    See Section 13.1.20.11, “Setting NDB_TABLE Options”, for further information.

    Note

    An equivalent method set_data_node_neighbour() is provided for use in NDB API applications.

  • ndb_dbg_check_shares

    Command-Line Format --ndb-dbg-check-shares=#
    Introduced 8.0.13-ndb-8.0.13
    System Variable ndb_dbg_check_shares
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    When set to 1, check that no shares are lingering. Available in debug builds only.

    Added in NDB 8.0.13.

  • ndb_default_column_format

    Command-Line Format --ndb-default-column-format={FIXED|DYNAMIC}
    System Variable ndb_default_column_format
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value FIXED
    Valid Values

    FIXED

    DYNAMIC

    Sets the default COLUMN_FORMAT and ROW_FORMAT for new tables (see Section 13.1.20, “CREATE TABLE Statement”). The default is FIXED.

  • ndb_deferred_constraints

    Command-Line Format --ndb-deferred-constraints=#
    System Variable ndb_deferred_constraints
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    Controls whether or not constraint checks are deferred, where these are supported. 0 is the default.

    This variable is not normally needed for operation of NDB Cluster or NDB Cluster Replication, and is intended primarily for use in testing.

  • ndb_distribution

    Command-Line Format --ndb-distribution={KEYHASH|LINHASH}
    System Variable ndb_distribution
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value KEYHASH
    Valid Values

    LINHASH

    KEYHASH

    Controls the default distribution method for NDB tables. Can be set to either of KEYHASH (key hashing) or LINHASH (linear hashing). KEYHASH is the default.

  • ndb_eventbuffer_free_percent

    Command-Line Format --ndb-eventbuffer-free-percent=#
    System Variable ndb_eventbuffer_free_percent
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 20
    Minimum Value 1
    Maximum Value 99

    Sets the percentage of the maximum memory allocated to the event buffer (ndb_eventbuffer_max_alloc) that should be available in event buffer after reaching the maximum, before starting to buffer again.

  • ndb_eventbuffer_max_alloc

    Command-Line Format --ndb-eventbuffer-max-alloc=#
    System Variable ndb_eventbuffer_max_alloc
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Sets the maximum amount memory (in bytes) that can be allocated for buffering events by the NDB API. 0 means that no limit is imposed, and is the default.

  • ndb_extra_logging

    Command-Line Format ndb_extra_logging=#
    System Variable ndb_extra_logging
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 1

    This variable enables recording in the MySQL error log of information specific to the NDB storage engine.

    When this variable is set to 0, the only information specific to NDB that is written to the MySQL error log relates to transaction handling. If it set to a value greater than 0 but less than 10, NDB table schema and connection events are also logged, as well as whether or not conflict resolution is in use, and other NDB errors and information. If the value is set to 10 or more, information about NDB internals, such as the progress of data distribution among cluster nodes, is also written to the MySQL error log. The default is 1.

  • ndb_force_send

    Command-Line Format --ndb-force-send[={OFF|ON}]
    System Variable ndb_force_send
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    Forces sending of buffers to NDB immediately, without waiting for other threads. Defaults to ON.

  • ndb_fully_replicated

    Command-Line Format --ndb-fully-replicated[={OFF|ON}]
    System Variable ndb_fully_replicated
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Determines whether new NDB tables are fully replicated. This setting can be overridden for an individual table using COMMENT="NDB_TABLE=FULLY_REPLICATED=..." in a CREATE TABLE or ALTER TABLE statement; see Section 13.1.20.11, “Setting NDB_TABLE Options”, for syntax and other information.

  • ndb_index_stat_enable

    Command-Line Format --ndb-index-stat-enable[={OFF|ON}]
    System Variable ndb_index_stat_enable
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    Use NDB index statistics in query optimization. The default is ON.

  • ndb_index_stat_option

    Command-Line Format --ndb-index-stat-option=value
    System Variable ndb_index_stat_option
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type String
    Default Value loop_checkon=1000ms,loop_idle=1000ms,loop_busy=100ms, update_batch=1,read_batch=4,idle_batch=32,check_batch=32, check_delay=1m,delete_batch=8,clean_delay=0,error_batch=4, error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M, cache_lowpct=90

    This variable is used for providing tuning options for NDB index statistics generation. The list consist of comma-separated name-value pairs of option names and values, and this list must not contain any space characters.

    Options not used when setting ndb_index_stat_option are not changed from their default values. For example, you can set ndb_index_stat_option = 'loop_idle=1000ms,cache_limit=32M'.

    Time values can be optionally suffixed with h (hours), m (minutes), or s (seconds). Millisecond values can optionally be specified using ms; millisecond values cannot be specified using h, m, or s.) Integer values can be suffixed with K, M, or G.

    The names of the options that can be set using this variable are shown in the table that follows. The table also provides brief descriptions of the options, their default values, and (where applicable) their minimum and maximum values.

    Table 23.20 ndb_index_stat_option options and values

    Name Description Default/Units Minimum/Maximum
    loop_enable 1000 ms 0/4G
    loop_idle Time to sleep when idle 1000 ms 0/4G
    loop_busy Time to sleep when more work is waiting 100 ms 0/4G
    update_batch 1 0/4G
    read_batch 4 1/4G
    idle_batch 32 1/4G
    check_batch 8 1/4G
    check_delay How often to check for new statistics 10 m 1/4G
    delete_batch 8 0/4G
    clean_delay 1 m 0/4G
    error_batch 4 1/4G
    error_delay 1 m 1/4G
    evict_batch 8 1/4G
    evict_delay Clean LRU cache, from read time 1 m 0/4G
    cache_limit Maximum amount of memory in bytes used for cached index statistics by this mysqld; clean up the cache when this is exceeded. 32 M 0/4G
    cache_lowpct 90 0/100
    zero_total Setting this to 1 resets all accumulating counters in ndb_index_stat_status to 0. This option value is also reset to 0 when this is done. 0 0/1

  • ndb_join_pushdown

    System Variable ndb_join_pushdown
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    This variable controls whether joins on NDB tables are pushed down to the NDB kernel (data nodes). Previously, a join was handled using multiple accesses of NDB by the SQL node; however, when ndb_join_pushdown is enabled, a pushable join is sent in its entirety to the data nodes, where it can be distributed among the data nodes and executed in parallel on multiple copies of the data, with a single, merged result being returned to mysqld. This can reduce greatly the number of round trips between an SQL node and the data nodes required to handle such a join.

    By default, ndb_join_pushdown is enabled.

    Conditions for NDB pushdown joins.  In order for a join to be pushable, it must meet the following conditions:

    1. Only columns can be compared, and all columns to be joined must use exactly the same data type. This means that (for example) a join on an INT column and a BIGINT column also cannot be pushed down.

      Previously, expressions such as t1.a = t2.a + constant could not be pushed down. This restriction is lifted in NDB 8.0.18 and later. The result of any operations on any column to be compared must yield the same type as the column itself.

      Also beginning with NDB 8.0.18, expressions comparing columns from the same table can be pushed down. The columns (or the result of any operations on those columns) must be of exactly the same type, including the same signedness, length, character set and collation, precision, and scale, where these are applicable.

    2. Queries referencing BLOB or TEXT columns are not supported.

    3. Explicit locking is not supported; however, the NDB storage engine's characteristic implicit row-based locking is enforced.

      This means that a join using FOR UPDATE cannot be pushed down.

    4. In order for a join to be pushed down, child tables in the join must be accessed using one of the ref, eq_ref, or  const access methods, or some combination of these methods.

      Outer joined child tables can only be pushed using eq_ref.

      If the root of the pushed join is an eq_ref or const, only child tables joined by eq_ref can be appended. (A table joined by ref is likely to become the root of another pushed join.)

      If the query optimizer decides on Using join cache for a candidate child table, that table cannot be pushed as a child. However, it may be the root of another set of pushed tables.

    5. Joins referencing tables explicitly partitioned by [LINEAR] HASH, LIST, or RANGE currently cannot be pushed down.

    You can see whether a given join can be pushed down by checking it with EXPLAIN; when the join can be pushed down, you can see references to the pushed join in the Extra column of the output, as shown in this example:

    mysql> EXPLAIN
        ->     SELECT e.first_name, e.last_name, t.title, d.dept_name
        ->         FROM employees e
        ->         JOIN dept_emp de ON e.emp_no=de.emp_no
        ->         JOIN departments d ON d.dept_no=de.dept_no
        ->         JOIN titles t ON e.emp_no=t.emp_no\G
    *************************** 1. row ***************************
               id: 1
      select_type: SIMPLE
            table: d
             type: ALL
    possible_keys: PRIMARY
              key: NULL
          key_len: NULL
              ref: NULL
             rows: 9
            Extra: Parent of 4 pushed join@1
    *************************** 2. row ***************************
               id: 1
      select_type: SIMPLE
            table: de
             type: ref
    possible_keys: PRIMARY,emp_no,dept_no
              key: dept_no
          key_len: 4
              ref: employees.d.dept_no
             rows: 5305
            Extra: Child of 'd' in pushed join@1
    *************************** 3. row ***************************
               id: 1
      select_type: SIMPLE
            table: e
             type: eq_ref
    possible_keys: PRIMARY
              key: PRIMARY
          key_len: 4
              ref: employees.de.emp_no
             rows: 1
            Extra: Child of 'de' in pushed join@1
    *************************** 4. row ***************************
               id: 1
      select_type: SIMPLE
            table: t
             type: ref
    possible_keys: PRIMARY,emp_no
              key: emp_no
          key_len: 4
              ref: employees.de.emp_no
             rows: 19
            Extra: Child of 'e' in pushed join@1
    4 rows in set (0.00 sec)
    
    Note

    If inner joined child tables are joined by ref, and the result is ordered or grouped by a sorted index, this index cannot provide sorted rows, which forces writing to a sorted tempfile.

    Two additional sources of information about pushed join performance are available:

    1. The status variables Ndb_pushed_queries_defined, Ndb_pushed_queries_dropped, Ndb_pushed_queries_executed, and Ndb_pushed_reads.

    2. The counters in the ndbinfo.counters table that belong to the DBSPJ kernel block.

  • ndb_log_apply_status

    Command-Line Format --ndb-log-apply-status[={OFF|ON}]
    System Variable ndb_log_apply_status
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    A read-only variable which shows whether the server was started with the --ndb-log-apply-status option.

  • ndb_log_bin

    Command-Line Format --ndb-log-bin[={OFF|ON}]
    System Variable ndb_log_bin
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value (≥ 8.0.16-ndb-8.0.16) OFF
    Default Value (≤ 8.0.15-ndb-8.0.15) ON

    Causes updates to NDB tables to be written to the binary log. The setting for this variable has no effect if binary logging is not already enabled on the server using log_bin. In NDB 8.0.16 and later, ndb_log_bin defaults to 0 (FALSE).

  • ndb_log_binlog_index

    Command-Line Format --ndb-log-binlog-index[={OFF|ON}]
    System Variable ndb_log_binlog_index
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    Causes a mapping of epochs to positions in the binary log to be inserted into the ndb_binlog_index table. Setting this variable has no effect if binary logging is not already enabled for the server using log_bin. (In addition, ndb_log_bin must not be disabled.) ndb_log_binlog_index defaults to 1 (ON); normally, there is never any need to change this value in a production environment.

  • ndb_log_empty_epochs

    Command-Line Format --ndb-log-empty-epochs[={OFF|ON}]
    System Variable ndb_log_empty_epochs
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    When this variable is set to 0, epoch transactions with no changes are not written to the binary log, although a row is still written even for an empty epoch in ndb_binlog_index.

  • ndb_log_empty_update

    Command-Line Format --ndb-log-empty-update[={OFF|ON}]
    System Variable ndb_log_empty_update
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    When this variable is set to ON (1), update transactions with no changes are written to the binary log, even when log_slave_updates is enabled.

  • ndb_log_exclusive_reads

    Command-Line Format --ndb-log-exclusive-reads[={OFF|ON}]
    System Variable ndb_log_exclusive_reads
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value 0

    This variable determines whether primary key reads are logged with exclusive locks, which allows for NDB Cluster Replication conflict detection and resolution based on read conflicts. To enable these locks, set the value of ndb_log_exclusive_reads to 1. 0, which disables such locking, is the default.

    For more information, see Read conflict detection and resolution.

  • ndb_log_orig

    Command-Line Format --ndb-log-orig[={OFF|ON}]
    System Variable ndb_log_orig
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Shows whether the originating server ID and epoch are logged in the ndb_binlog_index table. Set using the --ndb-log-orig server option.

  • ndb_log_transaction_id

    System Variable ndb_log_transaction_id
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    This read-only, Boolean system variable shows whether a replica mysqld writes NDB transaction IDs in the binary log (required to use active-active NDB Cluster Replication with NDB$EPOCH_TRANS() conflict detection). To change the setting, use the --ndb-log-transaction-id option.

    ndb_log_transaction_id is not supported in mainline MySQL Server 8.0.

    For more information, see Section 23.6.11, “NDB Cluster Replication Conflict Resolution”.

  • ndb_metadata_check

    Command-Line Format --ndb-metadata-check[={OFF|ON}]
    Introduced 8.0.16-ndb-8.0.16
    System Variable ndb_metadata_check
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    Beginning with NDB 8.0.16, NDB uses a background thread to check for metadata changes each ndb_metadata_check_interval seconds as compared with the MySQL data dictionary. This metadata change detection thread can be disabled by setting ndb_metadata_check to OFF. The thread is enabled by default.

  • ndb_metadata_check_interval

    Command-Line Format --ndb-metadata-check-interval=#
    Introduced 8.0.16-ndb-8.0.16
    System Variable ndb_metadata_check_interval
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 60
    Minimum Value 0
    Maximum Value 31536000
    Unit seconds

    In NDB 8.0.16 and later, NDB runs a metadata change detection thread in the background to determine when the NDB dictionary has changed with respect to the MySQL data dictionary. By default,the interval between such checks is 60 seconds; this can be adjusted by setting the value of ndb_metadata_check_interval. To enable or disable the thread, use ndb_metadata_check.

  • ndb_metadata_sync

    Introduced 8.0.19-ndb-8.0.19
    System Variable ndb_metadata_sync
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value false

    Setting this variable causes the change monitor thread to override any values set for ndb_metadata_check or ndb_metadata_check_interval, and to enter a period of continuous change detection. When the thread ascertains that there are no more changes to be detected, it stalls until the binary logging thread has finished synchronization of all detected objects. ndb_metadata_sync is then set to false, and the change monitor thread reverts to the behavior determined by the settings for ndb_metadata_check and ndb_metadata_check_interval.

    In NDB 8.0.22 and later, setting this variable to true causes the list of excluded objects to be cleared, and setting it to false clears the list of objects to be retried.

  • ndb_optimized_node_selection

    Command-Line Format --ndb-optimized-node-selection=#
    System Variable ndb_optimized_node_selection
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 3
    Minimum Value 0
    Maximum Value 3

    There are two forms of optimized node selection, described here:

    1. The SQL node uses promixity to determine the transaction coordinator; that is, the closest data node to the SQL node is chosen as the transaction coordinator. For this purpose, a data node having a shared memory connection with the SQL node is considered to be closest to the SQL node; the next closest (in order of decreasing proximity) are: TCP connection to localhost, followed by TCP connection from a host other than localhost.

    2. The SQL thread uses distribution awareness to select the data node. That is, the data node housing the cluster partition accessed by the first statement of a given transaction is used as the transaction coordinator for the entire transaction. (This is effective only if the first statement of the transaction accesses no more than one cluster partition.)

    This option takes one of the integer values 0, 1, 2, or 3. 3 is the default. These values affect node selection as follows:

    • 0: Node selection is not optimized. Each data node is employed as the transaction coordinator 8 times before the SQL thread proceeds to the next data node.

    • 1: Proximity to the SQL node is used to determine the transaction coordinator.

    • 2: Distribution awareness is used to select the transaction coordinator. However, if the first statement of the transaction accesses more than one cluster partition, the SQL node reverts to the round-robin behavior seen when this option is set to 0.

    • 3: If distribution awareness can be employed to determine the transaction coordinator, then it is used; otherwise proximity is used to select the transaction coordinator. (This is the default behavior.)

    Proximity is determined as follows:

    1. Start with the value set for the Group parameter (default 55).

    2. For an API node sharing the same host with other API nodes, decrement the value by 1. Assuming the default value for Group, the effective value for data nodes on same host as the API node is 54, and for remote data nodes 55.

    3. Setting ndb_data_node_neighbour further decreases the effective Group value by 50, causing this node to be regarded as the nearest node. This is needed only when all data nodes are on hosts other than that hosts the API node and it is desirable to dedicate one of them to the API node. In normal cases, the default adjustment described previously is sufficient.

    Frequent changes in ndb_data_node_neighbour are not advisable, since this changes the state of the cluster connection and thus may disrupt the selection algorithm for new transactions from each thread until it stablilizes.

  • ndb_read_backup

    Command-Line Format --ndb-read-backup[={OFF|ON}]
    System Variable ndb_read_backup
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value (≥ 8.0.19-ndb-8.0.19) ON
    Default Value (≤ 8.0.18-ndb-8.0.18) OFF

    Enable read from any fragment replica for any NDB table subsequently created; doing so greatly improves the table read performance at a relatively small cost to writes.

    To enable or disable read from any fragment replica for an individual table, you can set the NDB_TABLE option READ_BACKUP for the table accordingly, in a CREATE TABLE or ALTER TABLE statement; see Section 13.1.20.11, “Setting NDB_TABLE Options”, for more information.

  • ndb_recv_thread_activation_threshold

    Command-Line Format --ndb-recv-thread-activation-threshold=#
    System Variable ndb_recv_thread_activation_threshold
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 8
    Minimum Value 0 (MIN_ACTIVATION_THRESHOLD)
    Maximum Value 16 (MAX_ACTIVATION_THRESHOLD)

    When this number of concurrently active threads is reached, the receive thread takes over polling of the cluster connection.

    This variable is global in scope. It can also be set at startup.

  • ndb_recv_thread_cpu_mask

    Command-Line Format --ndb-recv-thread-cpu-mask=mask
    System Variable ndb_recv_thread_cpu_mask
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Bitmap
    Default Value [empty]

    CPU mask for locking receiver threads to specific CPUs. This is specified as a hexadecimal bitmask. For example, 0x33 means that one CPU is used per receiver thread. An empty string is the default; setting ndb_recv_thread_cpu_mask to this value removes any receiver thread locks previously set.

    This variable is global in scope. It can also be set at startup.

  • ndb_report_thresh_binlog_epoch_slip

    Command-Line Format --ndb-report-thresh-binlog-epoch-slip=#
    System Variable ndb_report_thresh_binlog_epoch_slip
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 10
    Minimum Value 0
    Maximum Value 256

    This represents the threshold for the number of epochs completely buffered in the event buffer, but not yet consumed by the binlog injector thread. When this degree of slippage (lag) is exceeded, an event buffer status message is reported, with BUFFERED_EPOCHS_OVER_THRESHOLD supplied as the reason (see Section 23.5.2.3, “Event Buffer Reporting in the Cluster Log”). Slip is increased when an epoch is received from data nodes and buffered completely in the event buffer; it is decreased when an epoch is consumed by the binlog injector thread, it is reduced. Empty epochs are buffered and queued, and so included in this calculation only when this is enabled using the Ndb::setEventBufferQueueEmptyEpoch() method from the NDB API.

  • ndb_report_thresh_binlog_mem_usage

    Command-Line Format --ndb-report-thresh-binlog-mem-usage=#
    System Variable ndb_report_thresh_binlog_mem_usage
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 10
    Minimum Value 0
    Maximum Value 10

    This is a threshold on the percentage of free memory remaining before reporting binary log status. For example, a value of 10 (the default) means that if the amount of available memory for receiving binary log data from the data nodes falls below 10%, a status message is sent to the cluster log.

  • ndb_row_checksum

    System Variable ndb_row_checksum
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 1
    Minimum Value 0
    Maximum Value 1

    Traditionally, NDB has created tables with row checksums, which checks for hardware issues at the expense of performance. Setting ndb_row_checksum to 0 means that row checksums are not used for new or altered tables, which has a significant impact on performance for all types of queries. This variable is set to 1 by default, to provide backward-compatible behavior.

  • ndb_schema_dist_lock_wait_timeout

    Command-Line Format --ndb-schema-dist-lock-wait-timeout=value
    Introduced 8.0.18-ndb-8.0.18
    System Variable ndb_schema_dist_lock_wait_timeout
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 30
    Minimum Value 0
    Maximum Value 1200
    Unit seconds

    Number of seconds to wait during schema distribution for the metadata lock taken on each SQL node in order to change its local data dictionary to reflect the DDL statement change. After this time has elapsed, a warning is returned to the effect that a given SQL node's data dictionary was not updated with the change. This avoids having the binary logging thread wait an excessive length of time while handling schema operations.

  • ndb_schema_dist_timeout

    Command-Line Format --ndb-schema-dist-timeout=value
    Introduced 8.0.16-ndb-8.0.16
    System Variable ndb_schema_dist_timeout
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 120
    Minimum Value 5
    Maximum Value 1200
    Unit seconds

    Number of seconds to wait before detecting a timeout during schema distribution. This can indicate that other SQL nodes are experiencing excessive activity, or that they are somehow being prevented from acquiring necessary resources at this time.

  • ndb_schema_dist_upgrade_allowed

    Command-Line Format --ndb-schema-dist-upgrade-allowed=value
    Introduced 8.0.17-ndb-8.0.17
    System Variable ndb_schema_dist_upgrade_allowed
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Boolean
    Default Value true

    Allow upgrading of the schema distribution table when connecting to NDB. When true (the default), this change is deferred until all SQL nodes have been upgraded to the same version of the NDB Cluster software.

    Note

    The performance of the schema distribution may be somewhat degraded until the upgrade has been performed.

  • ndb_show_foreign_key_mock_tables

    Command-Line Format --ndb-show-foreign-key-mock-tables[={OFF|ON}]
    System Variable ndb_show_foreign_key_mock_tables
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Show the mock tables used by NDB to support foreign_key_checks=0. When this is enabled, extra warnings are shown when creating and dropping the tables. The real (internal) name of the table can be seen in the output of SHOW CREATE TABLE.

  • ndb_slave_conflict_role

    Command-Line Format --ndb-slave-conflict-role=value
    Deprecated 8.0.23-ndb-8.0.23
    System Variable ndb_slave_conflict_role
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Enumeration
    Default Value NONE
    Valid Values

    NONE

    PRIMARY

    SECONDARY

    PASS

    Deprecated in NDB 8.0.23, and subject to removal in a future release. Use ndb_conflict_role instead.

  • ndb_table_no_logging

    System Variable ndb_table_no_logging
    Scope Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    When this variable is set to ON or 1, it causes NDB tables not to be checkpointed to disk. More specifically, this setting applies to tables which are created or altered using ENGINE NDB when ndb_table_no_logging is enabled, and continues to apply for the lifetime of the table, even if ndb_table_no_logging is later changed. Suppose that A, B, C, and D are tables that we create (and perhaps also alter), and that we also change the setting for ndb_table_no_logging as shown here:

    SET @@ndb_table_no_logging = 1;
    
    CREATE TABLE A ... ENGINE NDB;
    
    CREATE TABLE B ... ENGINE MYISAM;
    CREATE TABLE C ... ENGINE MYISAM;
    
    ALTER TABLE B ENGINE NDB;
    
    SET @@ndb_table_no_logging = 0;
    
    CREATE TABLE D ... ENGINE NDB;
    ALTER TABLE C ENGINE NDB;
    
    SET @@ndb_table_no_logging = 1;
    

    After the previous sequence of events, tables A and B are not checkpointed; A was created with ENGINE NDB and B was altered to use NDB, both while ndb_table_no_logging was enabled. However, tables C and D are logged; C was altered to use NDB and D was created using ENGINE NDB, both while ndb_table_no_logging was disabled. Setting ndb_table_no_logging back to 1 or ON does not cause table C or D to be checkpointed.

    Note

    ndb_table_no_logging has no effect on the creation of NDB table schema files; to suppress these, use ndb_table_temporary instead.

  • ndb_table_temporary

    System Variable ndb_table_temporary
    Scope Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    When set to ON or 1, this variable causes NDB tables not to be written to disk: This means that no table schema files are created, and that the tables are not logged.

    Note

    Setting this variable currently has no effect. This is a known issue; see Bug #34036.

  • ndb_use_copying_alter_table

    System Variable ndb_use_copying_alter_table
    Scope Global, Session
    Dynamic No
    SET_VAR Hint Applies No

    Forces NDB to use copying of tables in the event of problems with online ALTER TABLE operations. The default value is OFF.

  • ndb_use_exact_count

    System Variable ndb_use_exact_count
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Forces NDB to use a count of records during SELECT COUNT(*) query planning to speed up this type of query. The default value is OFF, which allows for faster queries overall.

  • ndb_use_transactions

    Command-Line Format --ndb-use-transactions[={OFF|ON}]
    System Variable ndb_use_transactions
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value ON

    You can disable NDB transaction support by setting this variable's values to OFF (not recommended). The default is ON.

  • ndb_version

    System Variable ndb_version
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type String
    Default Value

    NDB engine version, as a composite integer.

  • ndb_version_string

    System Variable ndb_version_string
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type String
    Default Value

    NDB engine version in ndb-x.y.z format.

  • server_id_bits

    Command-Line Format --server-id-bits=#
    System Variable server_id_bits
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type Integer
    Default Value 32
    Minimum Value 7
    Maximum Value 32

    This variable indicates the number of least significant bits within the 32-bit server_id which actually identify the server. Indicating that the server is actually identified by fewer than 32 bits makes it possible for some of the remaining bits to be used for other purposes, such as storing user data generated by applications using the NDB API's Event API within the AnyValue of an OperationOptions structure (NDB Cluster uses the AnyValue to store the server ID).

    When extracting the effective server ID from server_id for purposes such as detection of replication loops, the server ignores the remaining bits. The server_id_bits variable is used to mask out any irrelevant bits of server_id in the I/O and SQL threads when deciding whether an event should be ignored based on the server ID.

    This data can be read from the binary log by mysqlbinlog, provided that it is run with its own server_id_bits variable set to 32 (the default).

    If the value of server_id greater than or equal to 2 to the power of server_id_bits; otherwise, mysqld refuses to start.

    This system variable is supported only by NDB Cluster. It is not supported in the standard MySQL 8.0 Server.

  • slave_allow_batching

    Command-Line Format --slave-allow-batching[={OFF|ON}]
    System Variable slave_allow_batching
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Whether or not batched updates are enabled on NDB Cluster replicas.

    Setting this variable has an effect only when using replication with the NDB storage engine; in MySQL Server 8.0, it is present but does nothing. For more information, see Section 23.6.6, “Starting NDB Cluster Replication (Single Replication Channel)”.

  • transaction_allow_batching

    System Variable transaction_allow_batching
    Scope Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    When set to 1 or ON, this variable enables batching of statements within the same transaction. To use this variable, autocommit must first be disabled by setting it to 0 or OFF; otherwise, setting transaction_allow_batching has no effect.

    It is safe to use this variable with transactions that performs writes only, as having it enabled can lead to reads from the before image. You should ensure that any pending transactions are committed (using an explicit COMMIT if desired) before issuing a SELECT.

    Important

    transaction_allow_batching should not be used whenever there is the possibility that the effects of a given statement depend on the outcome of a previous statement within the same transaction.

    This variable is currently supported for NDB Cluster only.

The system variables in the following list all relate to the ndbinfo information database.

  • ndbinfo_database

    System Variable ndbinfo_database
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type String
    Default Value ndbinfo

    Shows the name used for the NDB information database; the default is ndbinfo. This is a read-only variable whose value is determined at compile time.

  • ndbinfo_max_bytes

    Command-Line Format --ndbinfo-max-bytes=#
    System Variable ndbinfo_max_bytes
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 0

    Used in testing and debugging only.

  • ndbinfo_max_rows

    Command-Line Format --ndbinfo-max-rows=#
    System Variable ndbinfo_max_rows
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Integer
    Default Value 10

    Used in testing and debugging only.

  • ndbinfo_offline

    System Variable ndbinfo_offline
    Scope Global
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF

    Place the ndbinfo database into offline mode, in which tables and views can be opened even when they do not actually exist, or when they exist but have different definitions in NDB. No rows are returned from such tables (or views).

  • ndbinfo_show_hidden

    Command-Line Format --ndbinfo-show-hidden[={OFF|ON}]
    System Variable ndbinfo_show_hidden
    Scope Global, Session
    Dynamic Yes
    SET_VAR Hint Applies No
    Type Boolean
    Default Value OFF
    Valid Values

    ON

    OFF

    Whether or not the ndbinfo database's underlying internal tables are shown in the mysql client. The default is OFF.

  • ndbinfo_table_prefix

    System Variable ndbinfo_table_prefix
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type String
    Default Value ndb$

    The prefix used in naming the ndbinfo database's base tables (normally hidden, unless exposed by setting ndbinfo_show_hidden). This is a read-only variable whose default value is ndb$; the prefix itself is determined at compile time.

  • ndbinfo_version

    System Variable ndbinfo_version
    Scope Global
    Dynamic No
    SET_VAR Hint Applies No
    Type String
    Default Value

    Shows the version of the ndbinfo engine in use; read-only.

23.3.3.9.3 NDB Cluster Status Variables

This section provides detailed information about MySQL server status variables that relate to NDB Cluster and the NDB storage engine. For status variables not specific to NDB Cluster, and for general information on using status variables, see Section 5.1.10, “Server Status Variables”.

23.3.3.10 NDB Cluster TCP/IP Connections

TCP/IP is the default transport mechanism for all connections between nodes in an NDB Cluster. Normally it is not necessary to define TCP/IP connections; NDB Cluster automatically sets up such connections for all data nodes, management nodes, and SQL or API nodes.

To override the default connection parameters, it is necessary to define a connection using one or more [tcp] sections in the config.ini file. Each [tcp] section explicitly defines a TCP/IP connection between two NDB Cluster nodes, and must contain at a minimum the parameters NodeId1 and NodeId2, as well as any connection parameters to override.

It is also possible to change the default values for these parameters by setting them in the [tcp default] section.

Important

Any [tcp] sections in the config.ini file should be listed last, following all other sections in the file. However, this is not required for a [tcp default] section. This requirement is a known issue with the way in which the config.ini file is read by the NDB Cluster management server.

Connection parameters which can be set in [tcp] and [tcp default] sections of the config.ini file are listed here:

  • AllowUnresolvedHostNames

    Version (or later) NDB 8.0.22
    Type or units boolean
    Default false
    Range true, false
    Restart Type N
    Added NDB 8.0.22

    By default, when a management node fails to resolve a host name while trying to connect, this results in a fatal error. This behavior can be overridden by setting AllowUnresolvedHostNames to true in the [tcp default] section of the global configuration file (usually named config.ini), in which case failure to resolve a host name is treated as a warning and ndb_mgmd startup continues uninterrupted.

  • Checksum

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    This parameter is a boolean parameter (enabled by setting it to Y or 1, disabled by setting it to N or 0). It is disabled by default. When it is enabled, checksums for all messages are calculated before they placed in the send buffer. This feature ensures that messages are not corrupted while waiting in the send buffer, or by the transport mechanism.

  • Group

    When ndb_optimized_node_selection is enabled, node proximity is used in some cases to select which node to connect to. This parameter can be used to influence proximity by setting it to a lower value, which is interpreted as closer. See the description of the system variable for more information.

  • HostName1

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    The HostName1 and HostName2 parameters can be used to specify specific network interfaces to be used for a given TCP connection between two nodes. The values used for these parameters can be host names or IP addresses.

  • HostName2

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    The HostName1 and HostName2 parameters can be used to specify specific network interfaces to be used for a given TCP connection between two nodes. The values used for these parameters can be host names or IP addresses.

  • NodeId1

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default [none]
    Range 1 - 255
    Restart Type N

    To identify a connection between two nodes it is necessary to provide their node IDs in the [tcp] section of the configuration file as the values of NodeId1 and NodeId2. These are the same unique Id values for each of these nodes as described in Section 23.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”.

  • NodeId2

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default [none]
    Range 1 - 255
    Restart Type N

    To identify a connection between two nodes it is necessary to provide their node IDs in the [tcp] section of the configuration file as the values of NodeId1 and NodeId2. These are the same unique Id values for each of these nodes as described in Section 23.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”.

  • OverloadLimit

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When more than this many unsent bytes are in the send buffer, the connection is considered overloaded.

    This parameter can be used to determine the amount of unsent data that must be present in the send buffer before the connection is considered overloaded. See Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”, for more information.

  • PreSendChecksum

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type S

    If this parameter and Checksum are both enabled, perform pre-send checksum checks, and check all TCP signals between nodes for errors. Has no effect if Checksum is not also enabled.

  • ReceiveBufferMemory

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 2M
    Range 16K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Specifies the size of the buffer used when receiving data from the TCP/IP socket.

    The default value of this parameter is 2MB. The minimum possible value is 16KB; the theoretical maximum is 4GB.

  • SendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 2M
    Range 256K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    TCP transporters use a buffer to store all messages before performing the send call to the operating system. When this buffer reaches 64KB its contents are sent; these are also sent when a round of messages have been executed. To handle temporary overload situations it is also possible to define a bigger send buffer.

    If this parameter is set explicitly, then the memory is not dedicated to each transporter; instead, the value used denotes the hard limit for how much memory (out of the total available memory—that is, TotalSendBufferMemory) that may be used by a single transporter. For more information about configuring dynamic transporter send buffer memory allocation in NDB Cluster, see Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”.

    The default size of the send buffer is 2MB, which is the size recommended in most situations. The minimum size is 64 KB; the theoretical maximum is 4 GB.

  • SendSignalId

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false (debug builds: true)
    Range true, false
    Restart Type N

    To be able to retrace a distributed message datagram, it is necessary to identify each message. When this parameter is set to Y, message IDs are transported over the network. This feature is disabled by default in production builds, and enabled in -debug builds.

  • TcpBind_INADDR_ANY

    Setting this parameter to TRUE or 1 binds IP_ADDR_ANY so that connections can be made from anywhere (for autogenerated connections). The default is FALSE (0).

  • TcpSpinTime

    Version (or later) NDB 8.0.20
    Type or units µsec
    Default 0
    Range 0 - 2000
    Restart Type N
    Added NDB 8.0.20

    Controls spin for a TCP transporter; no enable, set to a nonzero value. This works for both the data node and management or SQL node side of the connection.

  • TCP_MAXSEG_SIZE

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 2G
    Restart Type N

    Determines the size of the memory set during TCP transporter initialization. The default is recommended for most common usage cases.

  • TCP_RCV_BUF_SIZE

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 2G
    Restart Type N

    Determines the size of the receive buffer set during TCP transporter initialization. The default and minimum value is 0, which allows the operating system or platform to set this value. The default is recommended for most common usage cases.

  • TCP_SND_BUF_SIZE

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 2G
    Restart Type N

    Determines the size of the send buffer set during TCP transporter initialization. The default and minimum value is 0, which allows the operating system or platform to set this value. The default is recommended for most common usage cases.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.21 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.11 NDB Cluster TCP/IP Connections Using Direct Connections

Setting up a cluster using direct connections between data nodes requires specifying explicitly the crossover IP addresses of the data nodes so connected in the [tcp] section of the cluster config.ini file.

In the following example, we envision a cluster with at least four hosts, one each for a management server, an SQL node, and two data nodes. The cluster as a whole resides on the 172.23.72.* subnet of a LAN. In addition to the usual network connections, the two data nodes are connected directly using a standard crossover cable, and communicate with one another directly using IP addresses in the 1.1.0.* address range as shown:

# Management Server
[ndb_mgmd]
Id=1
HostName=172.23.72.20

# SQL Node
[mysqld]
Id=2
HostName=172.23.72.21

# Data Nodes
[ndbd]
Id=3
HostName=172.23.72.22

[ndbd]
Id=4
HostName=172.23.72.23

# TCP/IP Connections
[tcp]
NodeId1=3
NodeId2=4
HostName1=1.1.0.1
HostName2=1.1.0.2

The HostName1 and HostName2 parameters are used only when specifying direct connections.

The use of direct TCP connections between data nodes can improve the cluster's overall efficiency by enabling the data nodes to bypass an Ethernet device such as a switch, hub, or router, thus cutting down on the cluster's latency.

Note

To take the best advantage of direct connections in this fashion with more than two data nodes, you must have a direct connection between each data node and every other data node in the same node group.

23.3.3.12 NDB Cluster Shared-Memory Connections

Communications between NDB cluster nodes are normally handled using TCP/IP. The shared memory (SHM) transporter is distinguished by the fact that signals are transmitted by writing in memory rather than on a socket. The shared-memory transporter (SHM) can improve performance by negating up to 20% of the overhead required by a TCP connection when running an API node (usually an SQL node) and a data node together on the same host. You can enable a shared memory connection in either of the two ways listed here:

  • By setting the UseShm data node configuration parameter to 1, and setting HostName for the data node and HostName for the API node to the same value.

  • By using [shm] sections in the cluster configuration file, each containing settings for NodeId1 and NodeId2. This method is described in more detail later in this section.

Suppose a cluster is running a data node which has node ID 1 and an SQL node having node ID 51 on the same host computer at 10.0.0.1. To enable an SHM connection between these two nodes, all that is necessary is to insure that the following entries are included in the cluster configuration file:

[ndbd]
NodeId=1
HostName=10.0.0.1
UseShm=1

[mysqld]
NodeId=51
HostName=10.0.0.1
Important

The two entries just shown are in addition to any other entries and parameter settings needed by the cluster. A more complete example is shown later in this section.

Before starting data nodes that use SHM connections, it is also necessary to make sure that the operating system on each computer hosting such a data node has sufficient memory allocated to shared memory segments. See the documentation for your operating platform for information regarding this. In setups where multiple hosts are each running a data node and an API node, it is possible to enable shared memory on all such hosts by setting UseShm in the [ndbd default] section of the configuration file. This is shown in the example later in this section.

While not strictly required, tuning for all SHM connections in the cluster can be done by setting one or more of the following parameters in the [shm default] section of the cluster configuration (config.ini) file:

  • ShmSize: Shared memory size

  • ShmSpinTime: Time in µs to spin before sleeping

  • SendBufferMemory: Size of buffer for signals sent from this node, in bytes.

  • SendSignalId: Indicates that a signal ID is included in each signal sent through the transporter.

  • Checksum: Indicates that a checksum is included in each signal sent through the transporter.

  • PreSendChecksum: Checks of the checksum are made prior to sending the signal; Checksum must also be enabled for this to work

This example shows a simple setup with SHM connections definied on multiple hosts, in an NDB Cluster using 3 computers listed here by host name, hosting the node types shown:

  1. 10.0.0.0: The management server

  2. 10.0.0.1: A data node and an SQL node

  3. 10.0.0.2: A data node and an SQL node

In this scenario, each data node communicates with both the management server and the other data node using TCP transporters; each SQL node uses a shared memory transporter to communicate with the data nodes that is local to it, and a TCP transporter to communicate with the remote data node. A basic configuration reflecting this setup is enabled by the config.ini file whose contents are shown here:

[ndbd default]
DataDir=/path/to/datadir
UseShm=1

[shm default]
ShmSize=8M
ShmSpintime=200
SendBufferMemory=4M

[tcp default]
SendBufferMemory=8M

[ndb_mgmd]
NodeId=49
Hostname=10.0.0.0
DataDir=/path/to/datadir

[ndbd]
NodeId=1
Hostname=10.0.0.1
DataDir=/path/to/datadir

[ndbd]
NodeId=2
Hostname=10.0.0.2
DataDir=/path/to/datadir

[mysqld]
NodeId=51
Hostname=10.0.0.1

[mysqld]
NodeId=52
Hostname=10.0.0.2

[api]
[api]

Parameters affecting all shared memory transporters are set in the [shm default] section; these can be overridden on a per-connection basis in one or more [shm] sections. Each such section must be associated with a given SHM connection using NodeId1 and NodeId2; the values required for these parameters are the node IDs of the two nodes connected by the transporter. You can also identify the nodes by host name using HostName1 and HostName2, but these parameters are not required.

The API nodes for which no host names are set use the TCP transporter to communicate with data nodes independent of the hosts on which they are started; the parameters and values set in the [tcp default] section of the configuration file apply to all TCP transporters in the cluster.

For optimum performance, you can define a spin time for the SHM transporter (ShmSpinTime parameter); this affects both the data node receiver thread and the poll owner (receive thread or user thread) in NDB.

  • Checksum

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default true
    Range true, false
    Restart Type N

    This parameter is a boolean (Y/N) parameter which is disabled by default. When it is enabled, checksums for all messages are calculated before being placed in the send buffer.

    This feature prevents messages from being corrupted while waiting in the send buffer. It also serves as a check against data being corrupted during transport.

  • Group

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 35
    Range 0 - 200
    Restart Type N

    Determines the group proximity; a smaller value is interpreted as being closer. The default value is sufficient for most conditions.

  • HostName1

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    The HostName1 and HostName2 parameters can be used to specify specific network interfaces to be used for a given SHM connection between two nodes. The values used for these parameters can be host names or IP addresses.

  • HostName2

    Version (or later) NDB 8.0.13
    Type or units name or IP address
    Default [none]
    Range ...
    Restart Type N

    The HostName1 and HostName2 parameters can be used to specify specific network interfaces to be used for a given SHM connection between two nodes. The values used for these parameters can be host names or IP addresses.

  • NodeId1

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default [none]
    Range 1 - 255
    Restart Type N

    To identify a connection between two nodes it is necessary to provide node identifiers for each of them, as NodeId1 and NodeId2.

  • NodeId2

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default [none]
    Range 1 - 255
    Restart Type N

    To identify a connection between two nodes it is necessary to provide node identifiers for each of them, as NodeId1 and NodeId2.

  • NodeIdServer

    Version (or later) NDB 8.0.13
    Type or units numeric
    Default [none]
    Range 1 - 63
    Restart Type N

    Identify the server end of a shared memory connection. By default, this is the node ID of the data node.

  • OverloadLimit

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When more than this many unsent bytes are in the send buffer, the connection is considered overloaded. See Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”, and Section 23.5.14.55, “The ndbinfo transporters Table”, for more information.

  • PreSendChecksum

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type S

    If this parameter and Checksum are both enabled, perform pre-send checksum checks, and check all SHM signals between nodes for errors. Has no effect if Checksum is not also enabled.

  • SendBufferMemory

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 2M
    Range 256K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Size (in bytes) of the shared memory buffer for signals sent from this node using a shared memory connection.

  • SendSignalId

    Version (or later) NDB 8.0.13
    Type or units boolean
    Default false
    Range true, false
    Restart Type N

    To retrace the path of a distributed message, it is necessary to provide each message with a unique identifier. Setting this parameter to Y causes these message IDs to be transported over the network as well. This feature is disabled by default in production builds, and enabled in -debug builds.

  • ShmKey

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default 0
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N

    When setting up shared memory segments, a node ID, expressed as an integer, is used to identify uniquely the shared memory segment to use for the communication. There is no default value. If UseShm is enabled, the shared memory key is calculated automatically by NDB.

  • ShmSize

    Version (or later) NDB 8.0.13
    Type or units bytes
    Default 4M
    Range 64K - 4294967039 (0xFFFFFEFF)
    Restart Type N

    Each SHM connection has a shared memory segment where messages between nodes are placed by the sender and read by the reader. The size of this segment is defined by ShmSize. The default value is 4MB.

  • ShmSpinTime

    Version (or later) NDB 8.0.13
    Type or units integer
    Default 0
    Range 0 - 2000
    Restart Type S

    When receiving, the time to wait before sleeping, in microseconds.

  • SigNum

    Version (or later) NDB 8.0.13
    Type or units unsigned
    Default [none]
    Range 0 - 4294967039 (0xFFFFFEFF)
    Restart Type N
    Deprecated Yes (in NDB 7.6)

    This parameter was used formerly to override operating system signal numbers; in NDB 8.0, it is no longer used, and any setting for it is ignored.

Restart types.  Information about the restart types used by the parameter descriptions in this section is shown in the following table:

Table 23.22 NDB Cluster restart types

Symbol Restart Type Description
N Node The parameter can be updated using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”)
S System All cluster nodes must be shut down completely, then restarted, to effect a change in this parameter
I Initial Data nodes must be restarted using the --initial option

23.3.3.13 Data Node Memory Management

All memory allocation for a data node is performed when the node is started. This ensures that the data node can run in a stable manner without using swap memory, so that NDB can be used for latency-sensitive (realtime) applications. The following types of memory are allocated on data node startup:

  • Data memory

  • Shared global memory

  • Redo log buffers

  • Job buffers

  • Send buffers

  • Page cache for disk data records

  • Schema transaction memory

  • Transaction memory

  • Undo log buffer

  • Query memory

  • Block objects

  • Schema memory

  • Block data structures

  • Long signal memory

  • Shared memory communication buffers

The NDB memory manager, which regulates most data node memory, handles the following memory resources:

Each of these resources is set up with a reserved memory area and a maximum memory area. The reserved memory area can be used only by the resource for which it is reserved and cannot be shared with other resources; a given resource can never allocate more than the maximum memory allowed for the resource. A resource that has no maximum memory can expand to use all the shared memory in the memory manager.

The size of the global shared memory for these resources is controlled by the SharedGlobalMemory configuration parameter (default: 128 MB).

Data memory is always reserved and never acquires any memory from shared memory. It is controlled using the DataMemory configuration parameter, whose maximum is 16384 GB. DataMemory is where records are stored, including hash indexes (approximately 15 bytes per row), ordered indexes (10-12 bytes per row per index), and row headers (16-32 bytes per row).

Redo log buffers also use reserved memory only; this is controlled by the RedoBuffer configuration parameter, which sets the size of the redo log buffer per LDM thread. This means that the actual amount of memory used is the value of this parameter multiplied by the number of LDM threads in the data node.

Job buffers use reserved memory only; the size of this memory is calculated by NDB, based on the numbers of threads of various types.

Send buffers have a reserved part but can also allocate an additional 25% of shared global memory. The send buffer reserved size is calculated in two steps:

  1. Use the value of the TotalSendBufferMemory configuration parameter (no default value) or the sum of the individual send buffers used by all individual connections to the data node. A data node is connected to all other data nodes, to all API nodes, and to all management nodes. This means that, in a cluster with 2 data nodes, 2 management nodes, and 10 API nodes each data node has 13 node connections. Since the default value for SendBufferMemory for a data node connection is 2 MByte, this works out to 26 MB total.

  2. To obtain the total reserved size for the send buffer, the value of the ExtraSendBufferMemory configuration parameter, if any (default value 0). is added to the value obtained in the previous step.

In other words, if TotalSendBufferMemory has been set, the send buffer size is TotalSendBufferMemory + ExtraSendBufferMemory; otherwise, the size of the send buffer is equal to ([number of node connections] * SendBufferMemory) + ExtraSendBufferMemory.

The page cache for disk data records uses a reserved resource only; the size of this resource is controlled by the DiskPageBufferMemory configuration parameter (default 64 MB). Memory for 32 KB disk page entries is also allocated; the number of these is determined by the DiskPageBufferEntries configuration parameter (default 10).

Transaction memory has a reserved part that either is calculated by NDB, or is set explicitly using the TransactionMemory configuration parameter introduced in NDB 8.0.19 (in previous releases, this value was always calculated by NDB); transaction memory can also use an unlimited amount of shared global memory. Transaction memory is used for all operational resources handling transactions, scans, locks, scan buffers, and trigger operations. It also holds table rows as they are updated, before the next commit writes them to data memory.

In NDB 8.0.16 and earlier, operational records used dedicated resources whose sizes were controlled by a number of configuration parameters. Beginning with NDB 8.0.17, these are all allocated from a common transaction memory resource and can also use resources from global shared memory. In NDB 8.0.19 and later, the size of this resource can be controlled using a single TransactionMemory configuration parameter.

Reserved memory for undo log buffers can be set using the InitialLogFileGroup configuration parameter. If an undo log buffer is created as part of a CREATE LOGFILE GROUP SQL statement, the memory is taken from the transaction memory.

A number of resources relating to metadata for Disk Data resources also have no reserved part, and use shared global memory only. Shared global shared memory is thus shared between send buffers, transaction memory, and Disk Data metadata.

If TransactionMemory is not set, it is calculated based on the following parameters:

When TransactionMemory is set explicitly, none of the configuration parameters just listed are used to calculate memory size. In addition, the parameters MaxNoOfConcurrentIndexOperations, MaxNoOfFiredTriggers, MaxNoOfLocalOperations, and MaxNoOfLocalScans are incompatible with TransactionMemory and cannot be set concurrently with it; if TransactionMemory is set and any of these four parameters are also set in the config.ini configuration file, the management server cannot start. These four parameters are deprecated in NDB 8.0.19; expect them to be removed from a future release of MySQL NDB Cluster.

The transaction memory resource contains a large number of memory pools. Each memory pool represents an object type and contains a set of objects; each pool includes a reserved part allocated to the pool at startup; this reserved memory is never returned to shared global memory. Reserved records are found using a data structure having only a single level for fast retrieval, which means that a number of records in each pool should be reserved. The number of reserved records in each pool has some impact on performance and reserved memory allocation, but is generally necessary only in certain very advanced use cases to set the reserved sizes explicitly.

The size of the reserved part of the pool can be controlled by setting the following configuration parameters:

If the parameters just listed are not set, the reserved setting is 25% of transaction memory. The number of reserved records is per data node; these records are split among the threads handling them (LDM and TC threads) on each node. In most cases, it is sufficient to set TransactionMemory alone, and to allow the number of records in pools to be governed by its value.

MaxNoOfConcurrentScans limits the number of concurrent scans that can be active in each TC thread. This is important in guarding against cluster overload.

MaxNoOfConcurrentOperations limits the number of operations that can be active at any one time in updating transactions. (Simple reads are not affected by this parameter.) This number needs to be limited because it is necessary to preallocate memory for node failure handling, and a resource must be available for handling the maximum number of active operations in one TC thread when conmtending with node failures. It is imperative that MaxNoOfConcurrentOperations be set to the same number on all nodes (this can be done most easily by setting a value for it once, in the [ndbd default] section of the config.ini global configuration file). While its value can be increased using a rolling restart (see Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”), decreasing it in this way is not considered safe due to the possibility of a node failure occurring during the rolling restart.

It is possible to limit the size of a single transaction in NDB Cluster through the MaxDMLOperationsPerTransaction parameter. If this is not set, the size of one transaction is limited by MaxNoOfConcurrentOperations since this parameter limits the total number of concurrent operations per TC thread.

Schema memory size is controlled by the following set of configuration parameters:

The number of nodes and the number of LDM threads also have a major impact on the size of schema memory since the number of partitions in each table and each partition (and its fragment replicas) have to be represented in schema memory.

In addition, a number of other records are allocated during startup. These are relatively small. Each block in each thread contains block objects that use memory. This memory size is also normally quite small compared to the other data node memory structures.

23.3.3.14 Configuring NDB Cluster Send Buffer Parameters

The NDB kernel employs a unified send buffer whose memory is allocated dynamically from a pool shared by all transporters. This means that the size of the send buffer can be adjusted as necessary. Configuration of the unified send buffer can accomplished by setting the following parameters:

  • TotalSendBufferMemory.  This parameter can be set for all types of NDB Cluster nodes—that is, it can be set in the [ndbd], [mgm], and [api] (or [mysql]) sections of the config.ini file. It represents the total amount of memory (in bytes) to be allocated by each node for which it is set for use among all configured transporters. If set, its minimum is 256KB; the maximum is 4294967039.

    To be backward-compatible with existing configurations, this parameter takes as its default value the sum of the maximum send buffer sizes of all configured transporters, plus an additional 32KB (one page) per transporter. The maximum depends on the type of transporter, as shown in the following table:

    Table 23.23 Transporter types with maximum send buffer sizes

    Transporter Maximum Send Buffer Size (bytes)
    TCP SendBufferMemory (default = 2M)
    SHM 20K

    This enables existing configurations to function in close to the same way as they did with NDB Cluster 6.3 and earlier, with the same amount of memory and send buffer space available to each transporter. However, memory that is unused by one transporter is not available to other transporters.

  • OverloadLimit.  This parameter is used in the config.ini file [tcp] section, and denotes the amount of unsent data (in bytes) that must be present in the send buffer before the connection is considered overloaded. When such an overload condition occurs, transactions that affect the overloaded connection fail with NDB API Error 1218 (Send Buffers overloaded in NDB kernel) until the overload status passes. The default value is 0, in which case the effective overload limit is calculated as SendBufferMemory * 0.8 for a given connection. The maximum value for this parameter is 4G.

  • SendBufferMemory.  This value denotes a hard limit for the amount of memory that may be used by a single transporter out of the entire pool specified by TotalSendBufferMemory. However, the sum of SendBufferMemory for all configured transporters may be greater than the TotalSendBufferMemory that is set for a given node. This is a way to save memory when many nodes are in use, as long as the maximum amount of memory is never required by all transporters at the same time.

You can use the ndbinfo.transporters table to monitor send buffer memory usage, and to detect slowdown and overload conditions that can adversely affect performance.

23.3.4 Using High-Speed Interconnects with NDB Cluster

Even before design of NDBCLUSTER began in 1996, it was evident that one of the major problems to be encountered in building parallel databases would be communication between the nodes in the network. For this reason, NDBCLUSTER was designed from the very beginning to permit the use of a number of different data transport mechanisms. In this Manual, we use the term transporter for these.

The NDB Cluster codebase provides for four different transporters:

Most users today employ TCP/IP over Ethernet because it is ubiquitous. TCP/IP is also by far the best-tested transporter for use with NDB Cluster.

Regardless of the transporter used, NDB attempts to make sure that communication with data node processes is done using chunks that are as large as possible since this benefits all types of data transmission.

23.4 NDB Cluster Programs

23.4.1 ndbd — The NDB Cluster Data Node Daemon
23.4.2 ndbinfo_select_all — Select From ndbinfo Tables
23.4.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)
23.4.4 ndb_mgmd — The NDB Cluster Management Server Daemon
23.4.5 ndb_mgm — The NDB Cluster Management Client
23.4.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables
23.4.7 ndb_config — Extract NDB Cluster Configuration Information
23.4.8 ndb_delete_all — Delete All Rows from an NDB Table
23.4.9 ndb_desc — Describe NDB Tables
23.4.10 ndb_drop_index — Drop Index from an NDB Table
23.4.11 ndb_drop_table — Drop an NDB Table
23.4.12 ndb_error_reporter — NDB Error-Reporting Utility
23.4.13 ndb_import — Import CSV Data Into NDB
23.4.14 ndb_index_stat — NDB Index Statistics Utility
23.4.15 ndb_move_data — NDB Data Copy Utility
23.4.16 ndb_perror — Obtain NDB Error Message Information
23.4.17 ndb_print_backup_file — Print NDB Backup File Contents
23.4.18 ndb_print_file — Print NDB Disk Data File Contents
23.4.19 ndb_print_frag_file — Print NDB Fragment List File Contents
23.4.20 ndb_print_schema_file — Print NDB Schema File Contents
23.4.21 ndb_print_sys_file — Print NDB System File Contents
23.4.22 ndb_redo_log_reader — Check and Print Content of Cluster Redo Log
23.4.23 ndb_restore — Restore an NDB Cluster Backup
23.4.24 ndb_select_all — Print Rows from an NDB Table
23.4.25 ndb_select_count — Print Row Counts for NDB Tables
23.4.26 ndb_setup.py — Start browser-based Auto-Installer for NDB Cluster (DEPRECATED)
23.4.27 ndb_show_tables — Display List of NDB Tables
23.4.28 ndb_size.pl — NDBCLUSTER Size Requirement Estimator
23.4.29 ndb_top — View CPU usage information for NDB threads
23.4.30 ndb_waiter — Wait for NDB Cluster to Reach a Given Status
23.4.31 ndbxfrm — Compress, Decompress, Encrypt, and Decrypt Files Created by NDB Cluster
23.4.32 Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs

Using and managing an NDB Cluster requires several specialized programs, which we describe in this chapter. We discuss the purposes of these programs in an NDB Cluster, how to use the programs, and what startup options are available for each of them.

These programs include the NDB Cluster data, management, and SQL node processes (ndbd, ndbmtd, ndb_mgmd, and mysqld) and the management client (ndb_mgm).

Information about the program ndb_setup.py (now deprecated), used to start the NDB Cluster Auto-Installer, is also included in this section. You should be aware that Section 23.4.26, “ndb_setup.py — Start browser-based Auto-Installer for NDB Cluster (DEPRECATED)”, contains information about the command-line client only; for information about using the GUI installer spawned by this program to configure and deploy an NDB Cluster, see The NDB Cluster Auto-Installer (NDB 7.5) (No longer supported).

For information about using mysqld as an NDB Cluster process, see Section 23.5.9, “MySQL Server Usage for NDB Cluster”.

Other NDB utility, diagnostic, and example programs are included with the NDB Cluster distribution. These include ndb_restore, ndb_show_tables, and ndb_config. These programs are also covered in this section.

The final portion of this section contains tables of options that are common to all the various NDB Cluster programs.

23.4.1 ndbd — The NDB Cluster Data Node Daemon

ndbd is the process that is used to handle all the data in tables using the NDB Cluster storage engine. This is the process that empowers a data node to accomplish distributed transaction handling, node recovery, checkpointing to disk, online backup, and related tasks.

In an NDB Cluster, a set of ndbd processes cooperate in handling data. These processes can execute on the same computer (host) or on different computers. The correspondences between data nodes and Cluster hosts is completely configurable.

The following table includes command options specific to the NDB Cluster data node program ndbd. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndbd), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.24 Command-line options for the ndbd program

Format Description Added, Deprecated, or Removed

--bind-address=name

Local bind address

(Supported in all MySQL 8.0 based releases)

--connect-delay=#

Time to wait between attempts to contact a management server, in seconds; 0 means do not wait between attempts

(Supported in all MySQL 8.0 based releases)

--connect-retries=#

Set the number of times to retry a connection before giving up; 0 means 1 attempt only (and no retries)

(Supported in all MySQL 8.0 based releases)

--connect-retry-delay=#

Time to wait between attempts to contact a management server, in seconds; 0 means do not wait between attempts

(Supported in all MySQL 8.0 based releases)

--daemon,

-d

Start ndbd as daemon (default); override with --nodaemon

(Supported in all MySQL 8.0 based releases)

--foreground

Run ndbd in foreground, provided for debugging purposes (implies --nodaemon)

(Supported in all MySQL 8.0 based releases)

--initial

Perform initial start of ndbd, including file system cleanup; consult documentation before using this option

(Supported in all MySQL 8.0 based releases)

--initial-start

Perform partial initial start (requires --nowait-nodes)

(Supported in all MySQL 8.0 based releases)

--install[=name]

Used to install data node process as Windows service; does not apply on other platforms

(Supported in all MySQL 8.0 based releases)

--logbuffer-size=#

Control size of log buffer; for use when debugging with many log messages being generated; default is sufficient for normal operations

(Supported in all MySQL 8.0 based releases)

--nodaemon

Do not start ndbd as daemon; provided for testing purposes

(Supported in all MySQL 8.0 based releases)

--nostart,

-n

Do not start ndbd immediately; ndbd waits for command to start from ndb_mgm

(Supported in all MySQL 8.0 based releases)

--nowait-nodes=list

Do not wait for these data nodes to start (takes comma-separated list of node IDs); requires --ndb-nodeid

(Supported in all MySQL 8.0 based releases)

--remove[=name]

Used to remove data node process that was previously installed as Windows service; does not apply on other platforms

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Write extra debugging information to node log

(Supported in all MySQL 8.0 based releases)


Note

All of these options also apply to the multithreaded version of this program (ndbmtd) and you may substitute ndbmtd for ndbd wherever the latter occurs in this section.

  • --bind-address

    Command-Line Format --bind-address=name
    Type String
    Default Value

    Causes ndbd to bind to a specific network interface (host name or IP address). This option has no default value.

  • --connect-delay=#

    Command-Line Format --connect-delay=#
    Deprecated Yes
    Type Numeric
    Default Value 5
    Minimum Value 0
    Maximum Value 3600

    Determines the time to wait between attempts to contact a management server when starting (the number of attempts is controlled by the --connect-retries option). The default is 5 seconds.

    This option is deprecated, and is subject to removal in a future release of NDB Cluster. Use --connect-retry-delay instead.

  • --connect-retries=#

    Command-Line Format --connect-retries=#
    Type Numeric
    Default Value 12
    Minimum Value 0
    Maximum Value 65535

    Set the number of times to retry a connection before giving up; 0 means 1 attempt only (and no retries). The default is 12 attempts. The time to wait between attempts is controlled by the --connect-retry-delay option.

  • --connect-retry-delay=#

    Command-Line Format --connect-retry-delay=#
    Type Numeric
    Default Value 5
    Minimum Value 0
    Maximum Value 4294967295

    Determines the time to wait between attempts to contact a management server when starting (the time between attempts is controlled by the --connect-retries option). The default is 5 seconds.

    This option takes the place of the --connect-delay option, which is now deprecated and subject to removal in a future release of NDB Cluster.

  • --daemon, -d

    Command-Line Format --daemon
    Type Boolean
    Default Value TRUE

    Instructs ndbd or ndbmtd to execute as a daemon process. This is the default behavior. --nodaemon can be used to prevent the process from running as a daemon.

    This option has no effect when running ndbd or ndbmtd on Windows platforms.

  • --foreground

    Command-Line Format --foreground
    Type Boolean
    Default Value FALSE

    Causes ndbd or ndbmtd to execute as a foreground process, primarily for debugging purposes. This option implies the --nodaemon option.

    This option has no effect when running ndbd or ndbmtd on Windows platforms.

  • --initial

    Command-Line Format --initial
    Type Boolean
    Default Value FALSE

    Instructs ndbd to perform an initial start. An initial start erases any files created for recovery purposes by earlier instances of ndbd. It also re-creates recovery log files. On some operating systems, this process can take a substantial amount of time.

    An --initial start is to be used only when starting the ndbd process under very special circumstances; this is because this option causes all files to be removed from the NDB Cluster file system and all redo log files to be re-created. These circumstances are listed here:

    • When performing a software upgrade which has changed the contents of any files.

    • When restarting the node with a new version of ndbd.

    • As a measure of last resort when for some reason the node restart or system restart repeatedly fails. In this case, be aware that this node can no longer be used to restore data due to the destruction of the data files.

    Warning

    To avoid the possibility of eventual data loss, it is recommended that you not use the --initial option together with StopOnError = 0. Instead, set StopOnError to 0 in config.ini only after the cluster has been started, then restart the data nodes normally—that is, without the --initial option. See the description of the StopOnError parameter for a detailed explanation of this issue. (Bug #24945638)

    Use of this option prevents the StartPartialTimeout and StartPartitionedTimeout configuration parameters from having any effect.

    Important

    This option does not affect backup files that have already been created by the affected node.

    Prior to NDB 8.0.21, the --initial option also did not affect any Disk Data files. In NDB 8.0.21 and later, when used to perform an initial restart of the cluster, the option causes the removal of all data files associated with Disk Data tablespaces and undo log files associated with log file groups that existed previously on this data node (see Section 23.5.10, “NDB Cluster Disk Data Tables”).

    This option also has no effect on recovery of data by a data node that is just starting (or restarting) from data nodes that are already running (unless they also were started with --initial, as part of an initial restart). This recovery of data occurs automatically, and requires no user intervention in an NDB Cluster that is running normally.

    It is permissible to use this option when starting the cluster for the very first time (that is, before any data node files have been created); however, it is not necessary to do so.

  • --initial-start

    Command-Line Format --initial-start
    Type Boolean
    Default Value FALSE

    This option is used when performing a partial initial start of the cluster. Each node should be started with this option, as well as --nowait-nodes.

    Suppose that you have a 4-node cluster whose data nodes have the IDs 2, 3, 4, and 5, and you wish to perform a partial initial start using only nodes 2, 4, and 5—that is, omitting node 3:

    shell> ndbd --ndb-nodeid=2 --nowait-nodes=3 --initial-start
    shell> ndbd --ndb-nodeid=4 --nowait-nodes=3 --initial-start
    shell> ndbd --ndb-nodeid=5 --nowait-nodes=3 --initial-start
    

    When using this option, you must also specify the node ID for the data node being started with the --ndb-nodeid option.

    Important

    Do not confuse this option with the --nowait-nodes option for ndb_mgmd, which can be used to enable a cluster configured with multiple management servers to be started without all management servers being online.

  • --install[=name]

    Command-Line Format --install[=name]
    Platform Specific Windows
    Type String
    Default Value ndbd

    Causes ndbd to be installed as a Windows service. Optionally, you can specify a name for the service; if not set, the service name defaults to ndbd. Although it is preferable to specify other ndbd program options in a my.ini or my.cnf configuration file, it is possible to use together with --install. However, in such cases, the --install option must be specified first, before any other options are given, for the Windows service installation to succeed.

    It is generally not advisable to use this option together with the --initial option, since this causes the data node file system to be wiped and rebuilt every time the service is stopped and started. Extreme care should also be taken if you intend to use any of the other ndbd options that affect the starting of data nodes—including --initial-start, --nostart, and --nowait-nodes—together with --install, and you should make absolutely certain you fully understand and allow for any possible consequences of doing so.

    The --install option has no effect on non-Windows platforms.

  • --logbuffer-size=#

    Command-Line Format --logbuffer-size=#
    Type Integer
    Default Value 32768
    Minimum Value 2048
    Maximum Value 4294967295

    Sets the size of the data node log buffer. When debugging with high amounts of extra logging, it is possible for the log buffer to run out of space if there are too many log messages, in which case some log messages can be lost. This should not occur during normal operations.

  • --nodaemon

    Command-Line Format --nodaemon
    Type Boolean
    Default Value FALSE

    Prevents ndbd or ndbmtd from executing as a daemon process. This option overrides the --daemon option. This is useful for redirecting output to the screen when debugging the binary.

    The default behavior for ndbd and ndbmtd on Windows is to run in the foreground, making this option unnecessary on Windows platforms, where it has no effect.

  • --nostart, -n

    Command-Line Format --nostart
    Type Boolean
    Default Value FALSE

    Instructs ndbd not to start automatically. When this option is used, ndbd connects to the management server, obtains configuration data from it, and initializes communication objects. However, it does not actually start the execution engine until specifically requested to do so by the management server. This can be accomplished by issuing the proper START command in the management client (see Section 23.5.1, “Commands in the NDB Cluster Management Client”).

  • --nowait-nodes=node_id_1[, node_id_2[, ...]]

    Command-Line Format --nowait-nodes=list
    Type String
    Default Value

    This option takes a list of data nodes for which the cluster does not wait, prior to starting.

    This can be used to start the cluster in a partitioned state. For example, to start the cluster with only half of the data nodes (nodes 2, 3, 4, and 5) running in a 4-node cluster, you can start each ndbd process with --nowait-nodes=3,5. In this case, the cluster starts as soon as nodes 2 and 4 connect, and does not wait StartPartitionedTimeout milliseconds for nodes 3 and 5 to connect as it would otherwise.

    If you wanted to start up the same cluster as in the previous example without one ndbd (say, for example, that the host machine for node 3 has suffered a hardware failure) then start nodes 2, 4, and 5 with --nowait-nodes=3. Then the cluster starts as soon as nodes 2, 4, and 5 connect, and does not wait for node 3 to start.

  • --remove[=name]

    Command-Line Format --remove[=name]
    Platform Specific Windows
    Type String
    Default Value ndbd

    Causes an ndbd process that was previously installed as a Windows service to be removed. Optionally, you can specify a name for the service to be uninstalled; if not set, the service name defaults to ndbd.

    The --remove option has no effect on non-Windows platforms.

  • --verbose, -v

    Causes extra debug output to be written to the node log.

    You can also use NODELOG DEBUG ON and NODELOG DEBUG OFF to enable and disable this extra logging while the data node is running.

ndbd generates a set of log files which are placed in the directory specified by DataDir in the config.ini configuration file.

These log files are listed below. node_id is and represents the node's unique identifier. For example, ndb_2_error.log is the error log generated by the data node whose node ID is 2.

  • ndb_node_id_error.log is a file containing records of all crashes which the referenced ndbd process has encountered. Each record in this file contains a brief error string and a reference to a trace file for this crash. A typical entry in this file might appear as shown here:

    Date/Time: Saturday 30 July 2004 - 00:20:01
    Type of error: error
    Message: Internal program error (failed ndbrequire)
    Fault ID: 2341
    Problem data: DbtupFixAlloc.cpp
    Object of reference: DBTUP (Line: 173)
    ProgramName: NDB Kernel
    ProcessID: 14909
    TraceFile: ndb_2_trace.log.2
    ***EOM***
    

    Listings of possible ndbd exit codes and messages generated when a data node process shuts down prematurely can be found in Data Node Error Messages.

    Important

    The last entry in the error log file is not necessarily the newest one (nor is it likely to be). Entries in the error log are not listed in chronological order; rather, they correspond to the order of the trace files as determined in the ndb_node_id_trace.log.next file (see below). Error log entries are thus overwritten in a cyclical and not sequential fashion.

  • ndb_node_id_trace.log.trace_id is a trace file describing exactly what happened just before the error occurred. This information is useful for analysis by the NDB Cluster development team.

    It is possible to configure the number of these trace files that are created before old files are overwritten. trace_id is a number which is incremented for each successive trace file.

  • ndb_node_id_trace.log.next is the file that keeps track of the next trace file number to be assigned.

  • ndb_node_id_out.log is a file containing any data output by the ndbd process. This file is created only if ndbd is started as a daemon, which is the default behavior.

  • ndb_node_id.pid is a file containing the process ID of the ndbd process when started as a daemon. It also functions as a lock file to avoid the starting of nodes with the same identifier.

  • ndb_node_id_signal.log is a file used only in debug versions of ndbd, where it is possible to trace all incoming, outgoing, and internal messages with their data in the ndbd process.

It is recommended not to use a directory mounted through NFS because in some environments this can cause problems whereby the lock on the .pid file remains in effect even after the process has terminated.

To start ndbd, it may also be necessary to specify the host name of the management server and the port on which it is listening. Optionally, one may also specify the node ID that the process is to use.

shell> ndbd --connect-string="nodeid=2;host=ndb_mgmd.mysql.com:1186"

See Section 23.3.3.3, “NDB Cluster Connection Strings”, for additional information about this issue. Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”, describes other command-line options which can be used with ndbd. For information about data node configuration parameters, see Section 23.3.3.6, “Defining NDB Cluster Data Nodes”.

When ndbd starts, it actually initiates two processes. The first of these is called the angel process; its only job is to discover when the execution process has been completed, and then to restart the ndbd process if it is configured to do so. Thus, if you attempt to kill ndbd using the Unix kill command, it is necessary to kill both processes, beginning with the angel process. The preferred method of terminating an ndbd process is to use the management client and stop the process from there.

The execution process uses one thread for reading, writing, and scanning data, as well as all other activities. This thread is implemented asynchronously so that it can easily handle thousands of concurrent actions. In addition, a watch-dog thread supervises the execution thread to make sure that it does not hang in an endless loop. A pool of threads handles file I/O, with each thread able to handle one open file. Threads can also be used for transporter connections by the transporters in the ndbd process. In a multi-processor system performing a large number of operations (including updates), the ndbd process can consume up to 2 CPUs if permitted to do so.

For a machine with many CPUs it is possible to use several ndbd processes which belong to different node groups; however, such a configuration is still considered experimental and is not supported for MySQL 8.0 in a production setting. See Section 23.1.7, “Known Limitations of NDB Cluster”.

23.4.2 ndbinfo_select_all — Select From ndbinfo Tables

ndbinfo_select_all is a client program that selects all rows and columns from one or more tables in the ndbinfo database

Not all ndbinfo tables available in the mysql client can be read by this program. In addition, ndbinfo_select_all can show information about some tables internal to ndbinfo which cannot be accessed using SQL, including the tables and columns metadata tables.

To select from one or more ndbinfo tables using ndbinfo_select_all, it is necessary to supply the names of the tables when invoking the program as shown here:

shell> ndbinfo_select_all table_name1  [table_name2] [...]

For example:

shell> ndbinfo_select_all logbuffers logspaces
== logbuffers ==
node_id log_type        log_id  log_part        total   used    high
5       0       0       0       33554432        262144  0
6       0       0       0       33554432        262144  0
7       0       0       0       33554432        262144  0
8       0       0       0       33554432        262144  0
== logspaces ==
node_id log_type        log_id  log_part        total   used    high
5       0       0       0       268435456       0       0
5       0       0       1       268435456       0       0
5       0       0       2       268435456       0       0
5       0       0       3       268435456       0       0
6       0       0       0       268435456       0       0
6       0       0       1       268435456       0       0
6       0       0       2       268435456       0       0
6       0       0       3       268435456       0       0
7       0       0       0       268435456       0       0
7       0       0       1       268435456       0       0
7       0       0       2       268435456       0       0
7       0       0       3       268435456       0       0
8       0       0       0       268435456       0       0
8       0       0       1       268435456       0       0
8       0       0       2       268435456       0       0
8       0       0       3       268435456       0       0
shell>

The following table includes options that are specific to ndbinfo_select_all. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndbinfo_select_all), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.25 Command-line options for the ndbinfo_select_all program

Format Description Added, Deprecated, or Removed

--delay=#

Set delay in seconds between loops

(Supported in all MySQL 8.0 based releases)

--loops=#,

-l

Set number of times to perform select

(Supported in all MySQL 8.0 based releases)

--database=db_name,

-d

Name of database where table is located

(Supported in all MySQL 8.0 based releases)

--parallelism=#,

-p

Set degree of parallelism

(Supported in all MySQL 8.0 based releases)


  • --delay=seconds

    Command-Line Format --delay=#
    Type Numeric
    Default Value 5
    Minimum Value 0
    Maximum Value MAX_INT

    This option sets the number of seconds to wait between executing loops. Has no effect if --loops is set to 0 or 1.

  • --loops=number, -l number

    Command-Line Format --loops=#
    Type Numeric
    Default Value 1
    Minimum Value 0
    Maximum Value MAX_INT

    This option sets the number of times to execute the select. Use --delay to set the time between loops.

23.4.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)

ndbmtd is a multithreaded version of ndbd, the process that is used to handle all the data in tables using the NDBCLUSTER storage engine. ndbmtd is intended for use on host computers having multiple CPU cores. Except where otherwise noted, ndbmtd functions in the same way as ndbd; therefore, in this section, we concentrate on the ways in which ndbmtd differs from ndbd, and you should consult Section 23.4.1, “ndbd — The NDB Cluster Data Node Daemon”, for additional information about running NDB Cluster data nodes that apply to both the single-threaded and multithreaded versions of the data node process.

Command-line options and configuration parameters used with ndbd also apply to ndbmtd. For more information about these options and parameters, see Section 23.4.1, “ndbd — The NDB Cluster Data Node Daemon”, and Section 23.3.3.6, “Defining NDB Cluster Data Nodes”, respectively.

ndbmtd is also file system-compatible with ndbd. In other words, a data node running ndbd can be stopped, the binary replaced with ndbmtd, and then restarted without any loss of data. (However, when doing this, you must make sure that MaxNoOfExecutionThreads is set to an apppriate value before restarting the node if you wish for ndbmtd to run in multithreaded fashion.) Similarly, an ndbmtd binary can be replaced with ndbd simply by stopping the node and then starting ndbd in place of the multithreaded binary. It is not necessary when switching between the two to start the data node binary using --initial.

Using ndbmtd differs from using ndbd in two key respects:

  1. Because ndbmtd runs by default in single-threaded mode (that is, it behaves like ndbd), you must configure it to use multiple threads. This can be done by setting an appropriate value in the config.ini file for the MaxNoOfExecutionThreads configuration parameter or the ThreadConfig configuration parameter. Using MaxNoOfExecutionThreads is simpler, but ThreadConfig offers more flexibility. For more information about these configuration parameters and their use, see Multi-Threading Configuration Parameters (ndbmtd).

  2. Trace files are generated by critical errors in ndbmtd processes in a somewhat different fashion from how these are generated by ndbd failures. These differences are discussed in more detail in the next few paragraphs.

Like ndbd, ndbmtd generates a set of log files which are placed in the directory specified by DataDir in the config.ini configuration file. Except for trace files, these are generated in the same way and have the same names as those generated by ndbd.

In the event of a critical error, ndbmtd generates trace files describing what happened just prior to the error' occurrence. These files, which can be found in the data node's DataDir, are useful for analysis of problems by the NDB Cluster Development and Support teams. One trace file is generated for each ndbmtd thread. The names of these files have the following pattern:

ndb_node_id_trace.log.trace_id_tthread_id,

In this pattern, node_id stands for the data node's unique node ID in the cluster, trace_id is a trace sequence number, and thread_id is the thread ID. For example, in the event of the failure of an ndbmtd process running as an NDB Cluster data node having the node ID 3 and with MaxNoOfExecutionThreads equal to 4, four trace files are generated in the data node's data directory. If the is the first time this node has failed, then these files are named ndb_3_trace.log.1_t1, ndb_3_trace.log.1_t2, ndb_3_trace.log.1_t3, and ndb_3_trace.log.1_t4. Internally, these trace files follow the same format as ndbd trace files.

The ndbd exit codes and messages that are generated when a data node process shuts down prematurely are also used by ndbmtd. See Data Node Error Messages, for a listing of these.

Note

It is possible to use ndbd and ndbmtd concurrently on different data nodes in the same NDB Cluster. However, such configurations have not been tested extensively; thus, we cannot recommend doing so in a production setting at this time.

23.4.4 ndb_mgmd — The NDB Cluster Management Server Daemon

The management server is the process that reads the cluster configuration file and distributes this information to all nodes in the cluster that request it. It also maintains a log of cluster activities. Management clients can connect to the management server and check the cluster's status.

The following table includes options that are specific to the NDB Cluster management server program ndb_mgmd. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_mgmd), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.26 Command-line options for the ndb_mgmd program

Format Description Added, Deprecated, or Removed

--bind-address=host

Local bind address

(Supported in all MySQL 8.0 based releases)

--cluster-config-suffix=name

Override defaults group suffix when reading cluster_config sections in my.cnf file; used in testing

ADDED: NDB 8.0.24

--config-cache[=TRUE|FALSE]

Enable management server configuration cache; true by default

(Supported in all MySQL 8.0 based releases)

--config-file=file,

-f

Specify cluster configuration file; also specify --reload or --initial to override configuration cache if present

(Supported in all MySQL 8.0 based releases)

--configdir=directory,

--config-dir=directory

Specify cluster management server configuration cache directory

(Supported in all MySQL 8.0 based releases)

--daemon,

-d

Run ndb_mgmd in daemon mode (default)

(Supported in all MySQL 8.0 based releases)

--initial

Causes management server to reload configuration data from configuration file, bypassing configuration cache

(Supported in all MySQL 8.0 based releases)

--install[=name]

Used to install management server process as Windows service; does not apply on other platforms

(Supported in all MySQL 8.0 based releases)

--interactive

Run ndb_mgmd in interactive mode (not officially supported in production; for testing purposes only)

(Supported in all MySQL 8.0 based releases)

--log-name=name

Name to use when writing cluster log messages applying to this node

(Supported in all MySQL 8.0 based releases)

--mycnf

Read cluster configuration data from my.cnf file

(Supported in all MySQL 8.0 based releases)

--no-nodeid-checks

Do not provide any node ID checks

(Supported in all MySQL 8.0 based releases)

--nodaemon

Do not run ndb_mgmd as a daemon

(Supported in all MySQL 8.0 based releases)

--nowait-nodes=list

Do not wait for management nodes specified when starting this management server; requires --ndb-nodeid option

(Supported in all MySQL 8.0 based releases)

--print-full-config,

-P

Print full configuration and exit

(Supported in all MySQL 8.0 based releases)

--reload

Causes management server to compare configuration file with configuration cache

(Supported in all MySQL 8.0 based releases)

--remove[=name]

Used to remove management server process that was previously installed as Windows service, optionally specifying name of service to be removed; does not apply on other platforms

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Write additional information to log

(Supported in all MySQL 8.0 based releases)


  • --bind-address=host

    Command-Line Format --bind-address=host
    Type String
    Default Value [none]

    Causes the management server to bind to a specific network interface (host name or IP address). This option has no default value.

  • cluster-config-suffix

    Command-Line Format --cluster-config-suffix=name
    Introduced 8.0.24-ndb-8.0.24
    Type String
    Default Value [none]

    Override defaults group suffix when reading cluster configuration sections in my.cnf; used in testing.

  • --config-cache

    Command-Line Format --config-cache[=TRUE|FALSE]
    Type Boolean
    Default Value TRUE

    This option, whose default value is 1 (or TRUE, or ON), can be used to disable the management server's configuration cache, so that it reads its configuration from config.ini every time it starts (see Section 23.3.3, “NDB Cluster Configuration Files”). You can do this by starting the ndb_mgmd process with any one of the following options:

    • --config-cache=0

    • --config-cache=FALSE

    • --config-cache=OFF

    • --skip-config-cache

    Using one of the options just listed is effective only if the management server has no stored configuration at the time it is started. If the management server finds any configuration cache files, then the --config-cache option or the --skip-config-cache option is ignored. Therefore, to disable configuration caching, the option should be used the first time that the management server is started. Otherwise—that is, if you wish to disable configuration caching for a management server that has already created a configuration cache—you must stop the management server, delete any existing configuration cache files manually, then restart the management server with --skip-config-cache (or with --config-cache set equal to 0, OFF, or FALSE).

    Configuration cache files are normally created in a directory named mysql-cluster under the installation directory (unless this location has been overridden using the --configdir option). Each time the management server updates its configuration data, it writes a new cache file. The files are named sequentially in order of creation using the following format:

    ndb_node-id_config.bin.seq-number
    

    node-id is the management server's node ID; seq-number is a sequence number, beginning with 1. For example, if the management server's node ID is 5, then the first three configuration cache files would, when they are created, be named ndb_5_config.bin.1, ndb_5_config.bin.2, and ndb_5_config.bin.3.

    If your intent is to purge or reload the configuration cache without actually disabling caching, you should start ndb_mgmd with one of the options --reload or --initial instead of --skip-config-cache.

    To re-enable the configuration cache, simply restart the management server, but without the --config-cache or --skip-config-cache option that was used previously to disable the configuration cache.

    ndb_mgmd does not check for the configuration directory (--configdir) or attempts to create one when --skip-config-cache is used. (Bug #13428853)

  • --config-file=filename, -f filename

    Command-Line Format --config-file=file
    Type File name
    Default Value [none]

    Instructs the management server as to which file it should use for its configuration file. By default, the management server looks for a file named config.ini in the same directory as the ndb_mgmd executable; otherwise the file name and location must be specified explicitly.

    This option has no default value, and is ignored unless the management server is forced to read the configuration file, either because ndb_mgmd was started with the --reload or --initial option, or because the management server could not find any configuration cache. This option is also read if ndb_mgmd was started with --config-cache=OFF. See Section 23.3.3, “NDB Cluster Configuration Files”, for more information.

  • --configdir=dir_name

    Command-Line Format

    --configdir=directory

    --config-dir=directory

    Type File name
    Default Value $INSTALLDIR/mysql-cluster

    Specifies the cluster management server's configuration cache directory. --config-dir is an alias for this option.

  • --daemon, -d

    Command-Line Format --daemon
    Type Boolean
    Default Value TRUE

    Instructs ndb_mgmd to start as a daemon process. This is the default behavior.

    This option has no effect when running ndb_mgmd on Windows platforms.

  • --initial

    Command-Line Format --initial
    Type Boolean
    Default Value FALSE

    Configuration data is cached internally, rather than being read from the cluster global configuration file each time the management server is started (see Section 23.3.3, “NDB Cluster Configuration Files”). Using the --initial option overrides this behavior, by forcing the management server to delete any existing cache files, and then to re-read the configuration data from the cluster configuration file and to build a new cache.

    This differs in two ways from the --reload option. First, --reload forces the server to check the configuration file against the cache and reload its data only if the contents of the file are different from the cache. Second, --reload does not delete any existing cache files.

    If ndb_mgmd is invoked with --initial but cannot find a global configuration file, the management server cannot start.

    When a management server starts, it checks for another management server in the same NDB Cluster and tries to use the other management server's configuration data. This behavior has implications when performing a rolling restart of an NDB Cluster with multiple management nodes. See Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”, for more information.

    When used together with the --config-file option, the cache is cleared only if the configuration file is actually found.

  • --install[=name]

    Command-Line Format --install[=name]
    Platform Specific Windows
    Type String
    Default Value ndb_mgmd

    Causes ndb_mgmd to be installed as a Windows service. Optionally, you can specify a name for the service; if not set, the service name defaults to ndb_mgmd. Although it is preferable to specify other ndb_mgmd program options in a my.ini or my.cnf configuration file, it is possible to use them together with --install. However, in such cases, the --install option must be specified first, before any other options are given, for the Windows service installation to succeed.

    It is generally not advisable to use this option together with the --initial option, since this causes the configuration cache to be wiped and rebuilt every time the service is stopped and started. Care should also be taken if you intend to use any other ndb_mgmd options that affect the starting of the management server, and you should make absolutely certain you fully understand and allow for any possible consequences of doing so.

    The --install option has no effect on non-Windows platforms.

  • --interactive

    Command-Line Format --interactive
    Type Boolean
    Default Value FALSE

    Starts ndb_mgmd in interactive mode; that is, an ndb_mgm client session is started as soon as the management server is running. This option does not start any other NDB Cluster nodes.

  • --log-name=name

    Command-Line Format --log-name=name
    Type String
    Default Value MgmtSrvr

    Provides a name to be used for this node in the cluster log.

  • --mycnf

    Command-Line Format --mycnf
    Type Boolean
    Default Value FALSE

    Read configuration data from the my.cnf file.

  • --no-nodeid-checks

    Command-Line Format --no-nodeid-checks
    Type Boolean
    Default Value FALSE

    Do not perform any checks of node IDs.

  • --nodaemon

    Command-Line Format --nodaemon
    Type Boolean
    Default Value FALSE

    Instructs ndb_mgmd not to start as a daemon process.

    The default behavior for ndb_mgmd on Windows is to run in the foreground, making this option unnecessary on Windows platforms.

  • --nowait-nodes

    Command-Line Format --nowait-nodes=list
    Type Numeric
    Default Value [none]
    Minimum Value 1
    Maximum Value 255

    When starting an NDB Cluster is configured with two management nodes, each management server normally checks to see whether the other ndb_mgmd is also operational and whether the other management server's configuration is identical to its own. However, it is sometimes desirable to start the cluster with only one management node (and perhaps to allow the other ndb_mgmd to be started later). This option causes the management node to bypass any checks for any other management nodes whose node IDs are passed to this option, permitting the cluster to start as though configured to use only the management node that was started.

    For purposes of illustration, consider the following portion of a config.ini file (where we have omitted most of the configuration parameters that are not relevant to this example):

    [ndbd]
    NodeId = 1
    HostName = 198.51.100.101
    
    [ndbd]
    NodeId = 2
    HostName = 198.51.100.102
    
    [ndbd]
    NodeId = 3
    HostName = 198.51.100.103
    
    [ndbd]
    NodeId = 4
    HostName = 198.51.100.104
    
    [ndb_mgmd]
    NodeId = 10
    HostName = 198.51.100.150
    
    [ndb_mgmd]
    NodeId = 11
    HostName = 198.51.100.151
    
    [api]
    NodeId = 20
    HostName = 198.51.100.200
    
    [api]
    NodeId = 21
    HostName = 198.51.100.201
    

    Assume that you wish to start this cluster using only the management server having node ID 10 and running on the host having the IP address 198.51.100.150. (Suppose, for example, that the host computer on which you intend to the other management server is temporarily unavailable due to a hardware failure, and you are waiting for it to be repaired.) To start the cluster in this way, use a command line on the machine at 198.51.100.150 to enter the following command:

    shell> ndb_mgmd --ndb-nodeid=10 --nowait-nodes=11
    

    As shown in the preceding example, when using --nowait-nodes, you must also use the --ndb-nodeid option to specify the node ID of this ndb_mgmd process.

    You can then start each of the cluster's data nodes in the usual way. If you wish to start and use the second management server in addition to the first management server at a later time without restarting the data nodes, you must start each data node with a connection string that references both management servers, like this:

    shell> ndbd -c 198.51.100.150,198.51.100.151
    

    The same is true with regard to the connection string used with any mysqld processes that you wish to start as NDB Cluster SQL nodes connected to this cluster. See Section 23.3.3.3, “NDB Cluster Connection Strings”, for more information.

    When used with ndb_mgmd, this option affects the behavior of the management node with regard to other management nodes only. Do not confuse it with the --nowait-nodes option used with ndbd or ndbmtd to permit a cluster to start with fewer than its full complement of data nodes; when used with data nodes, this option affects their behavior only with regard to other data nodes.

    Multiple management node IDs may be passed to this option as a comma-separated list. Each node ID must be no less than 1 and no greater than 255. In practice, it is quite rare to use more than two management servers for the same NDB Cluster (or to have any need for doing so); in most cases you need to pass to this option only the single node ID for the one management server that you do not wish to use when starting the cluster.

    Note

    When you later start the missing management server, its configuration must match that of the management server that is already in use by the cluster. Otherwise, it fails the configuration check performed by the existing management server, and does not start.

  • --print-full-config, -P

    Command-Line Format --print-full-config
    Type Boolean
    Default Value FALSE

    Shows extended information regarding the configuration of the cluster. With this option on the command line the ndb_mgmd process prints information about the cluster setup including an extensive list of the cluster configuration sections as well as parameters and their values. Normally used together with the --config-file (-f) option.

  • --reload

    Command-Line Format --reload
    Type Boolean
    Default Value FALSE

    NDB Cluster configuration data is stored internally rather than being read from the cluster global configuration file each time the management server is started (see Section 23.3.3, “NDB Cluster Configuration Files”). Using this option forces the management server to check its internal data store against the cluster configuration file and to reload the configuration if it finds that the configuration file does not match the cache. Existing configuration cache files are preserved, but not used.

    This differs in two ways from the --initial option. First, --initial causes all cache files to be deleted. Second, --initial forces the management server to re-read the global configuration file and construct a new cache.

    If the management server cannot find a global configuration file, then the --reload option is ignored.

    When --reload is used, the management server must be able to communicate with data nodes and any other management servers in the cluster before it attempts to read the global configuration file; otherwise, the management server fails to start. This can happen due to changes in the networking environment, such as new IP addresses for nodes or an altered firewall configuration. In such cases, you must use --initial instead to force the exsiting cached configuration to be discarded and reloaded from the file. See Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”, for additional information.

  • --remove{=name]

    Command-Line Format --remove[=name]
    Platform Specific Windows
    Type String
    Default Value ndb_mgmd

    Remove a management server process that has been installed as a Windows service, optionally specifying the name of the service to be removed. Applies only to Windows platforms.

  • --verbose, -v

    Command-Line Format --verbose
    Type Boolean
    Default Value FALSE

    Remove a management server process that has been installed as a Windows service, optionally specifying the name of the service to be removed. Applies only to Windows platforms.

It is not strictly necessary to specify a connection string when starting the management server. However, if you are using more than one management server, a connection string should be provided and each node in the cluster should specify its node ID explicitly.

See Section 23.3.3.3, “NDB Cluster Connection Strings”, for information about using connection strings. Section 23.4.4, “ndb_mgmd — The NDB Cluster Management Server Daemon”, describes other options for ndb_mgmd.

The following files are created or used by ndb_mgmd in its starting directory, and are placed in the DataDir as specified in the config.ini configuration file. In the list that follows, node_id is the unique node identifier.

  • config.ini is the configuration file for the cluster as a whole. This file is created by the user and read by the management server. Section 23.3, “Configuration of NDB Cluster”, discusses how to set up this file.

  • ndb_node_id_cluster.log is the cluster events log file. Examples of such events include checkpoint startup and completion, node startup events, node failures, and levels of memory usage. A complete listing of cluster events with descriptions may be found in Section 23.5, “Management of NDB Cluster”.

    By default, when the size of the cluster log reaches one million bytes, the file is renamed to ndb_node_id_cluster.log.seq_id, where seq_id is the sequence number of the cluster log file. (For example: If files with the sequence numbers 1, 2, and 3 already exist, the next log file is named using the number 4.) You can change the size and number of files, and other characteristics of the cluster log, using the LogDestination configuration parameter.

  • ndb_node_id_out.log is the file used for stdout and stderr when running the management server as a daemon.

  • ndb_node_id.pid is the process ID file used when running the management server as a daemon.

23.4.5 ndb_mgm — The NDB Cluster Management Client

The ndb_mgm management client process is actually not needed to run the cluster. Its value lies in providing a set of commands for checking the cluster's status, starting backups, and performing other administrative functions. The management client accesses the management server using a C API. Advanced users can also employ this API for programming dedicated management processes to perform tasks similar to those performed by ndb_mgm.

To start the management client, it is necessary to supply the host name and port number of the management server:

shell> ndb_mgm [host_name [port_num]]

For example:

shell> ndb_mgm ndb_mgmd.mysql.com 1186

The default host name and port number are localhost and 1186, respectively.

The following table includes options that are specific to the NDB Cluster management client program ndb_mgm. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_mgm), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.27 Command-line options for the ndb_mgm program

Format Description Added, Deprecated, or Removed

--connect-retries=#

Set number of times to retry connection before giving up; 0 means 1 attempt only (and no retries)

(Supported in all MySQL 8.0 based releases)

--try-reconnect=#,

-t

Set number of times to retry connection before giving up; synonym for --connect-retries

(Supported in all MySQL 8.0 based releases)

--execute=name,

-e

Execute command and exit

(Supported in all MySQL 8.0 based releases)


  • --connect-retries=#

    Command-Line Format --connect-retries=#
    Type Numeric
    Default Value 3
    Minimum Value 0
    Maximum Value 4294967295

    This option specifies the number of times following the first attempt to retry a connection before giving up (the client always tries the connection at least once). The length of time to wait per attempt is set using --connect-retry-delay.

    This option is synonymous with the --try-reconnect option, which is now deprecated.

    The default for this option this option differs from its default when used with other NDB programs. See Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”, for more information.

  • --execute=command, -e command

    Command-Line Format --execute=name

    This option can be used to send a command to the NDB Cluster management client from the system shell. For example, either of the following is equivalent to executing SHOW in the management client:

    shell> ndb_mgm -e "SHOW"
    
    shell> ndb_mgm --execute="SHOW"
    

    This is analogous to how the --execute or -e option works with the mysql command-line client. See Section 4.2.2.1, “Using Options on the Command Line”.

    Note

    If the management client command to be passed using this option contains any space characters, then the command must be enclosed in quotation marks. Either single or double quotation marks may be used. If the management client command contains no space characters, the quotation marks are optional.

  • --try-reconnect=number

    Command-Line Format --try-reconnect=#
    Deprecated Yes
    Type Numeric
    Type Integer
    Default Value 12
    Default Value 3
    Minimum Value 0
    Maximum Value 4294967295

    If the connection to the management server is broken, the node tries to reconnect to it every 5 seconds until it succeeds. By using this option, it is possible to limit the number of attempts to number before giving up and reporting an error instead.

    This option is deprecated and subject to removal in a future release. Use --connect-retries, instead.

Additional information about using ndb_mgm can be found in Section 23.5.1, “Commands in the NDB Cluster Management Client”.

23.4.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster Tables

This tool can be used to check for and remove orphaned BLOB column parts from NDB tables, as well as to generate a file listing any orphaned parts. It is sometimes useful in diagnosing and repairing corrupted or damaged NDB tables containing BLOB or TEXT columns.

The basic syntax for ndb_blob_tool is shown here:

ndb_blob_tool [options] table [column, ...]

Unless you use the --help option, you must specify an action to be performed by including one or more of the options --check-orphans, --delete-orphans, or --dump-file. These options cause ndb_blob_tool to check for orphaned BLOB parts, remove any orphaned BLOB parts, and generate a dump file listing orphaned BLOB parts, respectively, and are described in more detail later in this section.

You must also specify the name of a table when invoking ndb_blob_tool. In addition, you can optionally follow the table name with the (comma-separated) names of one or more BLOB or TEXT columns from that table. If no columns are listed, the tool works on all of the table's BLOB and TEXT columns. If you need to specify a database, use the --database (-d) option.

The --verbose option provides additional information in the output about the tool's progress.

The following table includes options that are specific to ndb_blob_tool. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_blob_tool), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.28 Command-line options for the ndb_blob_tool program

Format Description Added, Deprecated, or Removed

--add-missing

Write dummy blob parts to take place of those which are missing

ADDED: NDB 8.0.20

--check-missing

Check for blobs having inline parts but missing one or more parts from parts table

ADDED: NDB 8.0.20

--check-orphans

Check for blob parts having no corresponding inline parts

(Supported in all MySQL 8.0 based releases)

--database=db_name,

-d

Database to find the table in

(Supported in all MySQL 8.0 based releases)

--delete-orphans

Delete blob parts having no corresponding inline parts

(Supported in all MySQL 8.0 based releases)

--dump-file=file

Write orphan keys to specified file

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Verbose output

(Supported in all MySQL 8.0 based releases)


  • --add-missing

    Command-Line Format --add-missing
    Introduced 8.0.20-ndb-8.0.20
    Type Boolean
    Default Value FALSE

    For each inline part in NDB Cluster tables which has no corresponding BLOB part, write a dummy BLOB part of the required length, consisting of spaces.

  • --check-missing

    Command-Line Format --check-missing
    Introduced 8.0.20-ndb-8.0.20
    Type Boolean
    Default Value FALSE

    Check for inline parts in NDB Cluster tables which have no corresponding BLOB parts.

  • --check-orphans

    Command-Line Format --check-orphans
    Type Boolean
    Default Value FALSE

    Check for BLOB parts in NDB Cluster tables which have no corresponding inline parts.

  • --database=db_name, -d

    Command-Line Format --database=db_name
    Type String
    Default Value [none]

    Specify the database to find the table in.

  • --delete-orphans

    Command-Line Format --delete-orphans
    Type Boolean
    Default Value FALSE

    Remove BLOB parts from NDB Cluster tables which have no corresponding inline parts.

  • --dump-file=file

    Command-Line Format --dump-file=file
    Type File name
    Default Value [none]

    Writes a list of orphaned BLOB column parts to file. The information written to the file includes the table key and BLOB part number for each orphaned BLOB part.

  • --verbose

    Command-Line Format --verbose
    Type Boolean
    Default Value FALSE

    Provide extra information in the tool's output regarding its progress.

Example

First we create an NDB table in the test database, using the CREATE TABLE statement shown here:

USE test;

CREATE TABLE btest (
    c0 BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    c1 TEXT,
    c2 BLOB
)   ENGINE=NDB;

Then we insert a few rows into this table, using a series of statements similar to this one:

INSERT INTO btest VALUES (NULL, 'x', REPEAT('x', 1000));

When run with --check-orphans against this table, ndb_blob_tool generates the following output:

shell> ndb_blob_tool --check-orphans --verbose -d test btest
connected
processing 2 blobs
processing blob #0 c1 NDB$BLOB_19_1
NDB$BLOB_19_1: nextResult: res=1
total parts: 0
orphan parts: 0
processing blob #1 c2 NDB$BLOB_19_2
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=0
NDB$BLOB_19_2: nextResult: res=1
total parts: 10
orphan parts: 0
disconnected

NDBT_ProgramExit: 0 - OK

The tool reports that there are no NDB BLOB column parts associated with column c1, even though c1 is a TEXT column. This is due to the fact that, in an NDB table, only the first 256 bytes of a BLOB or TEXT column value are stored inline, and only the excess, if any, is stored separately; thus, if there are no values using more than 256 bytes in a given column of one of these types, no BLOB column parts are created by NDB for this column. See Section 11.7, “Data Type Storage Requirements”, for more information.

23.4.7 ndb_config — Extract NDB Cluster Configuration Information

This tool extracts current configuration information for data nodes, SQL nodes, and API nodes from one of a number of sources: an NDB Cluster management node, or its config.ini or my.cnf file. By default, the management node is the source for the configuration data; to override the default, execute ndb_config with the --config-file or --mycnf option. It is also possible to use a data node as the source by specifying its node ID with --config_from_node=node_id.

ndb_config can also provide an offline dump of all configuration parameters which can be used, along with their default, maximum, and minimum values and other information. The dump can be produced in either text or XML format; for more information, see the discussion of the --configinfo and --xml options later in this section).

You can filter the results by section (DB, SYSTEM, or CONNECTIONS) using one of the options --nodes, --system, or --connections.

The following table includes options that are specific to ndb_config. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_config), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.29 Command-line options for the ndb_config program

Format Description Added, Deprecated, or Removed

--cluster-config-suffix=name

Override defaults group suffix when reading cluster_config sections in my.cnf file; used in testing

ADDED: NDB 8.0.24

--config-file=file_name

Set the path to config.ini file

(Supported in all MySQL 8.0 based releases)

--config-from-node=#

Obtain configuration data from the node having this ID (must be a data node)

(Supported in all MySQL 8.0 based releases)

--configinfo

Dumps information about all NDB configuration parameters in text format with default, maximum, and minimum values. Use with --xml to obtain XML output

(Supported in all MySQL 8.0 based releases)

--connections

Print connections information ([tcp], [tcp default], [sci], [sci default], [shm], or [shm default] sections of cluster configuration file) only. Cannot be used with --system or --nodes

(Supported in all MySQL 8.0 based releases)

--diff-default

Print only configuration parameters that have non-default values

(Supported in all MySQL 8.0 based releases)

--fields=string,

-f

Field separator

(Supported in all MySQL 8.0 based releases)

--host=name

Specify host

(Supported in all MySQL 8.0 based releases)

--mycnf

Read configuration data from my.cnf file

(Supported in all MySQL 8.0 based releases)

--nodeid

Get configuration of node with this ID

(Supported in all MySQL 8.0 based releases)

--nodes

Print node information ([ndbd] or [ndbd default] section of cluster configuration file) only. Cannot be used with --system or --connections

(Supported in all MySQL 8.0 based releases)

-c

Short form for --ndb-connectstring

(Supported in all MySQL 8.0 based releases)

--query=string,

-q

One or more query options (attributes)

(Supported in all MySQL 8.0 based releases)

--query-all,

-a

Dumps all parameters and values to a single comma-delimited string

(Supported in all MySQL 8.0 based releases)

--rows=string,

-r

Row separator

(Supported in all MySQL 8.0 based releases)

--system

Print SYSTEM section information only (see ndb_config --configinfo output). Cannot be used with --nodes or --connections

(Supported in all MySQL 8.0 based releases)

--type=name

Specify node type

(Supported in all MySQL 8.0 based releases)

--configinfo --xml

Use --xml with --configinfo to obtain a dump of all NDB configuration parameters in XML format with default, maximum, and minimum values

(Supported in all MySQL 8.0 based releases)


  • cluster-config-suffix

    Command-Line Format --cluster-config-suffix=name
    Introduced 8.0.24-ndb-8.0.24
    Type String
    Default Value [none]

    Override defaults group suffix when reading cluster configuration sections in my.cnf; used in testing.

  • --configinfo

    The --configinfo option causes ndb_config to dump a list of each NDB Cluster configuration parameter supported by the NDB Cluster distribution of which ndb_config is a part, including the following information:

    • A brief description of each parameter's purpose, effects, and usage

    • The section of the config.ini file where the parameter may be used

    • The parameter's data type or unit of measurement

    • Where applicable, the parameter's default, minimum, and maximum values

    • NDB Cluster release version and build information

    By default, this output is in text format. Part of this output is shown here:

    shell> ndb_config --configinfo
    
    ****** SYSTEM ******
    
    Name (String)
    Name of system (NDB Cluster)
    MANDATORY
    
    PrimaryMGMNode (Non-negative Integer)
    Node id of Primary ndb_mgmd(MGM) node
    Default: 0 (Min: 0, Max: 4294967039)
    
    ConfigGenerationNumber (Non-negative Integer)
    Configuration generation number
    Default: 0 (Min: 0, Max: 4294967039)
    
    ****** DB ******
    
    MaxNoOfSubscriptions (Non-negative Integer)
    Max no of subscriptions (default 0 == MaxNoOfTables)
    Default: 0 (Min: 0, Max: 4294967039)
    
    MaxNoOfSubscribers (Non-negative Integer)
    Max no of subscribers (default 0 == 2 * MaxNoOfTables)
    Default: 0 (Min: 0, Max: 4294967039)
    
    …
    

    Use this option together with the --xml option to obtain output in XML format.

  • --config-file=path-to-file

    Command-Line Format --config-file=file_name
    Type File name
    Default Value

    Gives the path to the management server's configuration file (config.ini). This may be a relative or absolute path. If the management node resides on a different host from the one on which ndb_config is invoked, then an absolute path must be used.

  • --config_from_node=#

    Command-Line Format --config-from-node=#
    Type Numeric
    Default Value none
    Minimum Value 1
    Maximum Value 48

    Obtain the cluster's configuration data from the data node that has this ID.

    If the node having this ID is not a data node, ndb_config fails with an error. (To obtain configuration data from the management node instead, simply omit this option.)

  • --connections

    Command-Line Format --connections
    Type Boolean
    Default Value FALSE

    Tells ndb_config to print CONNECTIONS information only—that is, information about parameters found in the [tcp], [tcp default], [shm], or [shm default] sections of the cluster configuration file (see Section 23.3.3.10, “NDB Cluster TCP/IP Connections”, and Section 23.3.3.12, “NDB Cluster Shared-Memory Connections”, for more information).

    This option is mutually exclusive with --nodes and --system; only one of these 3 options can be used.

  • --diff-default

    Command-Line Format --diff-default
    Type Boolean
    Default Value FALSE

    Print only configuration parameters that have non-default values.

  • --fields=delimiter, -f delimiter

    Command-Line Format --fields=string
    Type String
    Default Value

    Specifies a delimiter string used to separate the fields in the result. The default is , (the comma character).

    Note

    If the delimiter contains spaces or escapes (such as \n for the linefeed character), then it must be quoted.

  • --host=hostname

    Command-Line Format --host=name
    Type String
    Default Value

    Specifies the host name of the node for which configuration information is to be obtained.

    Note

    While the hostname localhost usually resolves to the IP address 127.0.0.1, this may not necessarily be true for all operating platforms and configurations. This means that it is possible, when localhost is used in config.ini, for ndb_config --host=localhost to fail if ndb_config is run on a different host where localhost resolves to a different address (for example, on some versions of SUSE Linux, this is 127.0.0.2). In general, for best results, you should use numeric IP addresses for all NDB Cluster configuration values relating to hosts, or verify that all NDB Cluster hosts handle localhost in the same fashion.

  • --mycnf

    Command-Line Format --mycnf
    Type Boolean
    Default Value FALSE

    Read configuration data from the my.cnf file.

  • --ndb-connectstring=connection_string, -c connection_string

    Command-Line Format

    --ndb-connectstring=connectstring

    --connect-string=connectstring

    Type String
    Default Value localhost:1186

    Specifies the connection string to use in connecting to the management server. The format for the connection string is the same as described in Section 23.3.3.3, “NDB Cluster Connection Strings”, and defaults to localhost:1186.

  • --nodeid=node_id

    Command-Line Format --ndb-nodeid=#
    Type Numeric
    Default Value 0

    Specify the node ID of the node for which configuration information is to be obtained.

  • --nodes

    Command-Line Format --nodes
    Type Boolean
    Default Value FALSE

    Tells ndb_config to print information relating only to parameters defined in an [ndbd] or [ndbd default] section of the cluster configuration file (see Section 23.3.3.6, “Defining NDB Cluster Data Nodes”).

    This option is mutually exclusive with --connections and --system; only one of these 3 options can be used.

  • --query=query-options, -q query-options

    Command-Line Format --query=string
    Type String
    Default Value

    This is a comma-delimited list of query options—that is, a list of one or more node attributes to be returned. These include nodeid (node ID), type (node type—that is, ndbd, mysqld, or ndb_mgmd), and any configuration parameters whose values are to be obtained.

    For example, --query=nodeid,type,datamemory,datadir returns the node ID, node type, DataMemory, and DataDir for each node.

    Note

    If a given parameter is not applicable to a certain type of node, than an empty string is returned for the corresponding value. See the examples later in this section for more information.

  • --query-all, -a

    Command-Line Format --query-all
    Type String
    Default Value

    Returns a comma-delimited list of all query options (node attributes; note that this list is a single string.

  • --rows=separator, -r separator

    Command-Line Format --rows=string
    Type String
    Default Value

    Specifies a separator string used to separate the rows in the result. The default is a space character.

    Note

    If the separator contains spaces or escapes (such as \n for the linefeed character), then it must be quoted.

  • --system

    Command-Line Format --system
    Type Boolean
    Default Value FALSE

    Tells ndb_config to print SYSTEM information only. This consists of system variables that cannot be changed at run time; thus, there is no corresponding section of the cluster configuration file for them. They can be seen (prefixed with ****** SYSTEM ******) in the output of ndb_config --configinfo.

    This option is mutually exclusive with --nodes and --connections; only one of these 3 options can be used.

  • --type=node_type

    Command-Line Format --type=name
    Type Enumeration
    Default Value [none]
    Valid Values

    ndbd

    mysqld

    ndb_mgmd

    Filters results so that only configuration values applying to nodes of the specified node_type (ndbd, mysqld, or ndb_mgmd) are returned.

  • --usage, --help, or -?

    Command-Line Format

    --help

    --usage

    Causes ndb_config to print a list of available options, and then exit.

  • --version, -V

    Command-Line Format --version

    Causes ndb_config to print a version information string, and then exit.

  • --configinfo --xml

    Command-Line Format --configinfo --xml
    Type Boolean
    Default Value false

    Cause ndb_config --configinfo to provide output as XML by adding this option. A portion of such output is shown in this example:

    shell> ndb_config --configinfo --xml
    
    <configvariables protocolversion="1" ndbversionstring="5.7.33-ndb-7.5.21"
                        ndbversion="460032" ndbversionmajor="7" ndbversionminor="5"
                        ndbversionbuild="0">
      <section name="SYSTEM">
        <param name="Name" comment="Name of system (NDB Cluster)" type="string"
                  mandatory="true"/>
        <param name="PrimaryMGMNode" comment="Node id of Primary ndb_mgmd(MGM) node"
                  type="unsigned" default="0" min="0" max="4294967039"/>
        <param name="ConfigGenerationNumber" comment="Configuration generation number"
                  type="unsigned" default="0" min="0" max="4294967039"/>
      </section>
      <section name="MYSQLD" primarykeys="NodeId">
        <param name="wan" comment="Use WAN TCP setting as default" type="bool"
                  default="false"/>
        <param name="HostName" comment="Name of computer for this node"
                  type="string" default=""/>
        <param name="Id" comment="NodeId" type="unsigned" mandatory="true"
                  min="1" max="255" deprecated="true"/>
        <param name="NodeId" comment="Number identifying application node (mysqld(API))"
                  type="unsigned" mandatory="true" min="1" max="255"/>
        <param name="ExecuteOnComputer" comment="HostName" type="string"
                  deprecated="true"/>
    
        …
    
      </section>
    
      …
    
    </configvariables>
    
    Note

    Normally, the XML output produced by ndb_config --configinfo --xml is formatted using one line per element; we have added extra whitespace in the previous example, as well as the next one, for reasons of legibility. This should not make any difference to applications using this output, since most XML processors either ignore nonessential whitespace as a matter of course, or can be instructed to do so.

    The XML output also indicates when changing a given parameter requires that data nodes be restarted using the --initial option. This is shown by the presence of an initial="true" attribute in the corresponding <param> element. In addition, the restart type (system or node) is also shown; if a given parameter requires a system restart, this is indicated by the presence of a restart="system" attribute in the corresponding <param> element. For example, changing the value set for the Diskless parameter requires a system initial restart, as shown here (with the restart and initial attributes highlighted for visibility):

    <param name="Diskless" comment="Run wo/ disk" type="bool" default="false"
              restart="system" initial="true"/>
    

    Currently, no initial attribute is included in the XML output for <param> elements corresponding to parameters which do not require initial restarts; in other words, initial="false" is the default, and the value false should be assumed if the attribute is not present. Similarly, the default restart type is node (that is, an online or rolling restart of the cluster), but the restart attribute is included only if the restart type is system (meaning that all cluster nodes must be shut down at the same time, then restarted).

    Deprecated parameters are indicated in the XML output by the deprecated attribute, as shown here:

    <param name="NoOfDiskPagesToDiskAfterRestartACC" comment="DiskCheckpointSpeed"
           type="unsigned" default="20" min="1" max="4294967039" deprecated="true"/>
    

    In such cases, the comment refers to one or more parameters that supersede the deprecated parameter. Similarly to initial, the deprecated attribute is indicated only when the parameter is deprecated, with deprecated="true", and does not appear at all for parameters which are not deprecated. (Bug #21127135)

    Beginning with NDB 7.5.0, parameters that are required are indicated with mandatory="true", as shown here:

    <param name="NodeId"
              comment="Number identifying application node (mysqld(API))"
              type="unsigned" mandatory="true" min="1" max="255"/>
    

    In much the same way that the initial or deprecated attribute is displayed only for a parameter that requires an intial restart or that is deprecated, the mandatory attribute is included only if the given parameter is actually required.

    Important

    The --xml option can be used only with the --configinfo option. Using --xml without --configinfo fails with an error.

    Unlike the options used with this program to obtain current configuration data, --configinfo and --xml use information obtained from the NDB Cluster sources when ndb_config was compiled. For this reason, no connection to a running NDB Cluster or access to a config.ini or my.cnf file is required for these two options.

Combining other ndb_config options (such as --query or --type) with --configinfo (with or without the --xml option is not supported. Currently, if you attempt to do so, the usual result is that all other options besides --configinfo or --xml are simply ignored. However, this behavior is not guaranteed and is subject to change at any time. In addition, since ndb_config, when used with the --configinfo option, does not access the NDB Cluster or read any files, trying to specify additional options such as --ndb-connectstring or --config-file with --configinfo serves no purpose.

Examples

  1. To obtain the node ID and type of each node in the cluster:

    shell> ./ndb_config --query=nodeid,type --fields=':' --rows='\n'
    1:ndbd
    2:ndbd
    3:ndbd
    4:ndbd
    5:ndb_mgmd
    6:mysqld
    7:mysqld
    8:mysqld
    9:mysqld
    

    In this example, we used the --fields options to separate the ID and type of each node with a colon character (:), and the --rows options to place the values for each node on a new line in the output.

  2. To produce a connection string that can be used by data, SQL, and API nodes to connect to the management server:

    shell> ./ndb_config --config-file=usr/local/mysql/cluster-data/config.ini \
    --query=hostname,portnumber --fields=: --rows=, --type=ndb_mgmd
    198.51.100.179:1186
    
  3. This invocation of ndb_config checks only data nodes (using the --type option), and shows the values for each node's ID and host name, as well as the values set for its DataMemory and DataDir parameters:

    shell> ./ndb_config --type=ndbd --query=nodeid,host,datamemory,datadir -f ' : ' -r '\n'
    1 : 198.51.100.193 : 83886080 : /usr/local/mysql/cluster-data
    2 : 198.51.100.112 : 83886080 : /usr/local/mysql/cluster-data
    3 : 198.51.100.176 : 83886080 : /usr/local/mysql/cluster-data
    4 : 198.51.100.119 : 83886080 : /usr/local/mysql/cluster-data
    

    In this example, we used the short options -f and -r for setting the field delimiter and row separator, respectively, as well as the short option -q to pass a list of parameters to be obtained.

  4. To exclude results from any host except one in particular, use the --host option:

    shell> ./ndb_config --host=198.51.100.176 -f : -r '\n' -q id,type
    3:ndbd
    5:ndb_mgmd
    

    In this example, we also used the short form -q to determine the attributes to be queried.

    Similarly, you can limit results to a node with a specific ID using the --nodeid option.

23.4.8 ndb_delete_all — Delete All Rows from an NDB Table

ndb_delete_all deletes all rows from the given NDB table. In some cases, this can be much faster than DELETE or even TRUNCATE TABLE.

Usage

ndb_delete_all -c connection_string tbl_name -d db_name

This deletes all rows from the table named tbl_name in the database named db_name. It is exactly equivalent to executing TRUNCATE db_name.tbl_name in MySQL.

The following table includes options that are specific to ndb_delete_all. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_delete_all), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.30 Command-line options for the ndb_delete_all program

Format Description Added, Deprecated, or Removed

--database=dbname,

-d

Name of the database in which the table is found

(Supported in all MySQL 8.0 based releases)

--transactional,

-t

Perform the delete in a single transaction (may run out of operations)

(Supported in all MySQL 8.0 based releases)

--tupscan

Run tup scan

(Supported in all MySQL 8.0 based releases)

--diskscan

Run disk scan

(Supported in all MySQL 8.0 based releases)


  • --transactional, -t

    Use of this option causes the delete operation to be performed as a single transaction.

    Warning

    With very large tables, using this option may cause the number of operations available to the cluster to be exceeded.

Prior to NDB 8.0.18, this program printed NDBT_ProgramExit - status upon completion of its run, due to an unnecessary dependency on the NDBT testing library. This dependency has been removed, eliminating the extraneous output.

23.4.9 ndb_desc — Describe NDB Tables

ndb_desc provides a detailed description of one or more NDB tables.

Usage

ndb_desc -c connection_string tbl_name -d db_name [options]

ndb_desc -c connection_string index_name -d db_name -t tbl_name

Additional options that can be used with ndb_desc are listed later in this section.

Sample Output

MySQL table creation and population statements:

USE test;

CREATE TABLE fish (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(20) NOT NULL,
    length_mm INT NOT NULL,
    weight_gm INT NOT NULL,

    PRIMARY KEY pk (id),
    UNIQUE KEY uk (name)
) ENGINE=NDB;

INSERT INTO fish VALUES
    (NULL, 'guppy', 35, 2), (NULL, 'tuna', 2500, 150000),
    (NULL, 'shark', 3000, 110000), (NULL, 'manta ray', 1500, 50000),
    (NULL, 'grouper', 900, 125000), (NULL ,'puffer', 250, 2500);

Output from ndb_desc:

shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 2
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 337
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
HashMap: DEFAULT-HASHMAP-3840-2
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition       Row count       Commit count    Frag fixed memory       Frag varsized memory    Extent_space    Free extent_space
0               2               2               32768                   32768                   0               0
1               4               4               32768                   32768                   0               0


NDBT_ProgramExit: 0 - OK

Information about multiple tables can be obtained in a single invocation of ndb_desc by using their names, separated by spaces. All of the tables must be in the same database.

You can obtain additional information about a specific index using the --table (short form: -t) option and supplying the name of the index as the first argument to ndb_desc, as shown here:

shell> ./ndb_desc uk -d test -t fish
-- uk --
Version: 2
Base table: fish
Number of attributes: 1
Logging: 0
Index type: OrderedIndex
Index status: Retrieved
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
-- IndexTable 10/uk --
Version: 2
Fragment type: FragUndefined
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: yes
Number of attributes: 2
Number of primary keys: 1
Length of frm data: 0
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 2
ForceVarPart: 0
PartitionCount: 2
FragmentCount: 2
FragmentCountType: ONE_PER_LDM_PER_NODE
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
-- Attributes --
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
NDB$TNODE Unsigned [64] PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
-- Indexes --
PRIMARY KEY(NDB$TNODE) - UniqueHashIndex

NDBT_ProgramExit: 0 - OK

When an index is specified in this way, the --extra-partition-info and --extra-node-info options have no effect.

The Version column in the output contains the table's schema object version. For information about interpreting this value, see NDB Schema Object Versions.

Three of the table properties that can be set using NDB_TABLE comments embedded in CREATE TABLE and ALTER TABLE statements are also visible in ndb_desc output. The table's FRAGMENT_COUNT_TYPE is always shown in the FragmentCountType column. READ_ONLY and FULLY_REPLICATED, if set to 1, are shown in the Table options column. You can see this after executing the following ALTER TABLE statement in the mysql client:

mysql> ALTER TABLE fish COMMENT='NDB_TABLE=READ_ONLY=1,FULLY_REPLICATED=1';
1 row in set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS\G
+---------+------+---------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                 |
+---------+------+---------------------------------------------------------------------------------------------------------+
| Warning | 1296 | Got error 4503 'Table property is FRAGMENT_COUNT_TYPE=ONE_PER_LDM_PER_NODE but not in comment' from NDB |
+---------+------+---------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

The warning is issued because READ_ONLY=1 requires that the table's fragment count type is (or be set to) ONE_PER_LDM_PER_NODE_GROUP; NDB sets this automatically in such cases. You can check that the ALTER TABLE statement has the desired effect using SHOW CREATE TABLE:

mysql> SHOW CREATE TABLE fish\G
*************************** 1. row ***************************
       Table: fish
Create Table: CREATE TABLE `fish` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `length_mm` int(11) NOT NULL,
  `weight_gm` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uk` (`name`)
) ENGINE=ndbcluster DEFAULT CHARSET=latin1
COMMENT='NDB_TABLE=READ_BACKUP=1,FULLY_REPLICATED=1'
1 row in set (0.01 sec)

Because FRAGMENT_COUNT_TYPE was not set explicitly, its value is not shown in the comment text printed by SHOW CREATE TABLE. ndb_desc, however, displays the updated value for this attribute. The Table options column shows the binary properties just enabled. You can see this in the output shown here (emphasized text):

shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 4
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 380
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 1
FragmentCount: 1
FragmentCountType: ONE_PER_LDM_PER_NODE_GROUP
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options: readbackup, fullyreplicated
HashMap: DEFAULT-HASHMAP-3840-1
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY DYNAMIC
length_mm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
weight_gm Int NOT NULL AT=FIXED ST=MEMORY DYNAMIC
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition       Row count       Commit count    Frag fixed memory       Frag varsized memory    Extent_space    Free extent_space

NDBT_ProgramExit: 0 - OK

For more information about these table properties, see Section 13.1.20.11, “Setting NDB_TABLE Options”.

The Extent_space and Free extent_space columns are applicable only to NDB tables having columns on disk; for tables having only in-memory columns, these columns always contain the value 0.

To illustrate their use, we modify the previous example. First, we must create the necessary Disk Data objects, as shown here:

CREATE LOGFILE GROUP lg_1
    ADD UNDOFILE 'undo_1.log'
    INITIAL_SIZE 16M
    UNDO_BUFFER_SIZE 2M
    ENGINE NDB;

ALTER LOGFILE GROUP lg_1
    ADD UNDOFILE 'undo_2.log'
    INITIAL_SIZE 12M
    ENGINE NDB;

CREATE TABLESPACE ts_1
    ADD DATAFILE 'data_1.dat'
    USE LOGFILE GROUP lg_1
    INITIAL_SIZE 32M
    ENGINE NDB;

ALTER TABLESPACE ts_1
    ADD DATAFILE 'data_2.dat'
    INITIAL_SIZE 48M
    ENGINE NDB;

(For more information on the statements just shown and the objects created by them, see Section 23.5.10.1, “NDB Cluster Disk Data Objects”, as well as Section 13.1.16, “CREATE LOGFILE GROUP Statement”, and Section 13.1.21, “CREATE TABLESPACE Statement”.)

Now we can create and populate a version of the fish table that stores 2 of its columns on disk (deleting the previous version of the table first, if it already exists):

DROP TABLE IF EXISTS fish;

CREATE TABLE fish (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(20) NOT NULL,
    length_mm INT NOT NULL,
    weight_gm INT NOT NULL,

    PRIMARY KEY pk (id),
    UNIQUE KEY uk (name)
) TABLESPACE ts_1 STORAGE DISK
ENGINE=NDB;

INSERT INTO fish VALUES
    (NULL, 'guppy', 35, 2), (NULL, 'tuna', 2500, 150000),
    (NULL, 'shark', 3000, 110000), (NULL, 'manta ray', 1500, 50000),
    (NULL, 'grouper', 900, 125000), (NULL ,'puffer', 250, 2500);

When run against this version of the table, ndb_desc displays the following output:

shell> ./ndb_desc -c localhost fish -d test -p
-- fish --
Version: 1
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 1001
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 2
FragmentCount: 2
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options: readbackup
HashMap: DEFAULT-HASHMAP-3840-2
Tablespace id: 16
Tablespace: ts_1
-- Attributes --
id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
name Varchar(80;utf8mb4_0900_ai_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
length_mm Int NOT NULL AT=FIXED ST=DISK
weight_gm Int NOT NULL AT=FIXED ST=DISK
-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex
uk(name) - OrderedIndex
uk$unique(name) - UniqueHashIndex
-- Per partition info --
Partition       Row count       Commit count    Frag fixed memory       Frag varsized memory    Extent_space    Free extent_space
0               2               2               32768                   32768                   1048576         1044440
1               4               4               32768                   32768                   1048576         1044400


NDBT_ProgramExit: 0 - OK

This means that 1048576 bytes are allocated from the tablespace for this table on each partition, of which 1044440 bytes remain free for additional storage. In other words, 1048576 - 1044440 = 4136 bytes per partition is currently being used to store the data from this table's disk-based columns. The number of bytes shown as Free extent_space is available for storing on-disk column data from the fish table only; for this reason, it is not visible when selecting from the INFORMATION_SCHEMA.FILES table.

Tablespace id and Tablespace are displayed for Disk Data tables beginning with NDB 8.0.21.

For fully replicated tables, ndb_desc shows only the nodes holding primary partition fragment replicas; nodes with copy fragment replicas (only) are ignored. You can obtain such information, using the mysql client, from the table_distribution_status, table_fragments, table_info, and table_replicas tables in the ndbinfo database.

The following table includes options that are specific to ndb_desc. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_desc), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.31 Command-line options for the ndb_desc program

Format Description Added, Deprecated, or Removed

--auto-inc,

-a

Show next value for AUTO_INCREMENT oolumn if table has one

ADDED: NDB 8.0.21

--blob-info,

-b

Include partition information for BLOB tables in output. Requires that the -p option also be used

(Supported in all MySQL 8.0 based releases)

--context,

-x

Show extra information for table such as database, schema, name, internal ID

ADDED: NDB 8.0.21

--database=dbname,

-d

Name of database containing table

(Supported in all MySQL 8.0 based releases)

--extra-node-info,

-n

Include partition-to-data-node mappings in output. Requires that the -p option also be used

(Supported in all MySQL 8.0 based releases)

--extra-partition-info,

-p

Display information about partitions

(Supported in all MySQL 8.0 based releases)

--retries=#,

-r

Number of times to retry the connection (once per second)

(Supported in all MySQL 8.0 based releases)

--table=tbl_name,

-t

Specify the table in which to find an index. When this option is used, -p and -n have no effect and are ignored

(Supported in all MySQL 8.0 based releases)

--unqualified,

-u

Use unqualified table names

(Supported in all MySQL 8.0 based releases)


  • --auto-inc, -a

    Show the next value for a table's AUTO_INCREMENT column, if it has one.

  • --blob-info, -b

    Include information about subordinate BLOB and TEXT columns.

    Use of this option also requires the use of the --extra-partition-info (-p) option.

  • --context, -x

    Show additional contextual information for the table such as schema, database name, table name, and the table's internal ID.

  • --database=db_name, -d

    Specify the database in which the table should be found.

  • --extra-node-info, -n

    Include information about the mappings between table partitions and the data nodes upon which they reside. This information can be useful for verifying distribution awareness mechanisms and supporting more efficient application access to the data stored in NDB Cluster.

    Use of this option also requires the use of the --extra-partition-info (-p) option.

  • --extra-partition-info, -p

    Print additional information about the table's partitions.

  • --retries=#, -r

    Try to connect this many times before giving up. One connect attempt is made per second.

  • --table=tbl_name, -t

    Specify the table in which to look for an index.

  • --unqualified, -u

    Use unqualified table names.

Table indexes listed in the output are ordered by ID.

23.4.10 ndb_drop_index — Drop Index from an NDB Table

ndb_drop_index drops the specified index from an NDB table. It is recommended that you use this utility only as an example for writing NDB API applications—see the Warning later in this section for details.

Usage

ndb_drop_index -c connection_string table_name index -d db_name

The statement shown above drops the index named index from the table in the database.

The following table includes options that are specific to ndb_drop_index. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_drop_index), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.32 Command-line options for the ndb_drop_index program

Format Description Added, Deprecated, or Removed

--database=dbname,

-d

Name of database in which table is found

(Supported in all MySQL 8.0 based releases)


Warning

Operations performed on Cluster table indexes using the NDB API are not visible to MySQL and make the table unusable by a MySQL server. If you use this program to drop an index, then try to access the table from an SQL node, an error results, as shown here:

shell> ./ndb_drop_index -c localhost dogs ix -d ctest1
Dropping index dogs/idx...OK

NDBT_ProgramExit: 0 - OK

shell> ./mysql -u jon -p ctest1
Enter password: *******
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7 to server version: 5.7.33-ndb-7.5.21

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> SHOW TABLES;
+------------------+
| Tables_in_ctest1 |
+------------------+
| a                |
| bt1              |
| bt2              |
| dogs             |
| employees        |
| fish             |
+------------------+
6 rows in set (0.00 sec)

mysql> SELECT * FROM dogs;
ERROR 1296 (HY000): Got error 4243 'Index not found' from NDBCLUSTER

In such a case, your only option for making the table available to MySQL again is to drop the table and re-create it. You can use either the SQL statementDROP TABLE or the ndb_drop_table utility (see Section 23.4.11, “ndb_drop_table — Drop an NDB Table”) to drop the table.

23.4.11 ndb_drop_table — Drop an NDB Table

ndb_drop_table drops the specified NDB table. (If you try to use this on a table created with a storage engine other than NDB, the attempt fails with the error 723: No such table exists.) This operation is extremely fast; in some cases, it can be an order of magnitude faster than using a MySQL DROP TABLE statement on an NDB table.

Usage

ndb_drop_table -c connection_string tbl_name -d db_name

The following table includes options that are specific to ndb_drop_table. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_drop_table), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.33 Command-line options for the ndb_drop_table program

Format Description Added, Deprecated, or Removed

--database=dbname,

-d

Name of database in which table is found

(Supported in all MySQL 8.0 based releases)


Prior to NDB 8.0.17, an NDB table dropped using this utility persisted in the MySQL data dictionary but could not be dropped using DROP TABLE in the mysql client. In NDB 8.0.17 and later, such orphan tables can be dropped using DROP TABLE. (Bug #29125206, Bug #93672)

23.4.12 ndb_error_reporter — NDB Error-Reporting Utility

ndb_error_reporter creates an archive from data node and management node log files that can be used to help diagnose bugs or other problems with a cluster. It is highly recommended that you make use of this utility when filing reports of bugs in NDB Cluster.

The following table includes command options specific to the NDB Cluster program ndb_error_reporter. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_error_reporter), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.34 Command-line options for the ndb_error_reporter program

Format Description Added, Deprecated, or Removed

--connection-timeout=timeout

Number of seconds to wait when connecting to nodes before timing out

(Supported in all MySQL 8.0 based releases)

--dry-scp

Disable scp with remote hosts; used only for testing

(Supported in all MySQL 8.0 based releases)

--fs

Include file system data in error report; can use a large amount of disk space

(Supported in all MySQL 8.0 based releases)

--skip-nodegroup=nodegroup_id

Skip all nodes in the node group having this ID

(Supported in all MySQL 8.0 based releases)


Usage

ndb_error_reporter path/to/config-file [username] [options]

This utility is intended for use on a management node host, and requires the path to the management host configuration file (usually named config.ini). Optionally, you can supply the name of a user that is able to access the cluster's data nodes using SSH, to copy the data node log files. ndb_error_reporter then includes all of these files in archive that is created in the same directory in which it is run. The archive is named ndb_error_report_YYYYMMDDhhmmss.tar.bz2, where YYYYMMDDhhmmss is a datetime string.

ndb_error_reporter also accepts the options listed here:

  • --connection-timeout=timeout

    Command-Line Format --connection-timeout=timeout
    Type Integer
    Default Value 0

    Wait this many seconds when trying to connect to nodes before timing out.

  • --dry-scp

    Command-Line Format --dry-scp
    Type Boolean
    Default Value TRUE

    Run ndb_error_reporter without using scp from remote hosts. Used for testing only.

  • --fs

    Command-Line Format --fs
    Type Boolean
    Default Value FALSE

    Copy the data node file systems to the management host and include them in the archive.

    Because data node file systems can be extremely large, even after being compressed, we ask that you please do not send archives created using this option to Oracle unless you are specifically requested to do so.

  • --skip-nodegroup=nodegroup_id

    Command-Line Format --connection-timeout=timeout
    Type Integer
    Default Value 0

    Skip all nodes belong to the node group having the supplied node group ID.

23.4.13 ndb_import — Import CSV Data Into NDB

ndb_import imports CSV-formatted data, such as that produced by mysqldump --tab, directly into NDB using the NDB API. ndb_import requires a connection to an NDB management server (ndb_mgmd) to function; it does not require a connection to a MySQL Server.

Usage

ndb_import db_name file_name options

ndb_import requires two arguments. db_name is the name of the database where the table into which to import the data is found; file_name is the name of the CSV file from which to read the data; this must include the path to this file if it is not in the current directory. The name of the file must match that of the table; the file's extension, if any, is not taken into consideration. Options supported by ndb_import include those for specifying field separators, escapes, and line terminators, and are described later in this section. ndb_import must be able to connect to an NDB Cluster management server; for this reason, there must be an unused [api] slot in the cluster config.ini file.

To duplicate an existing table that uses a different storage engine, such as InnoDB, as an NDB table, use the mysql client to perform a SELECT INTO OUTFILE statement to export the existing table to a CSV file, then to execute a CREATE TABLE LIKE statement to create a new table having the same structure as the existing table, then perform ALTER TABLE ... ENGINE=NDB on the new table; after this, from the system shell, invoke ndb_import to load the data into the new NDB table. For example, an existing InnoDB table named myinnodb_table in a database named myinnodb can be exported into an NDB table named myndb_table in a database named myndb as shown here, assuming that you are already logged in as a MySQL user with the appropriate privileges:

  1. In the mysql client:

    mysql> USE myinnodb;
    
    mysql> SELECT * INTO OUTFILE '/tmp/myndb_table.csv'
         >  FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' ESCAPED BY '\\'
         >  LINES TERMINATED BY '\n'
         >  FROM myinnodbtable;
    
    mysql> CREATE DATABASE myndb;
    
    mysql> USE myndb;
    
    mysql> CREATE TABLE myndb_table LIKE myinnodb.myinnodb_table;
    
    mysql> ALTER TABLE myndb_table ENGINE=NDB;
    
    mysql> EXIT;
    Bye
    shell>
    

    Once the target database and table have been created, a running mysqld is no longer required. You can stop it using mysqladmin shutdown or another method before proceeding, if you wish.

  2. In the system shell:

    # if you are not already in the MySQL bin directory:
    shell> cd path-to-mysql-bin-dir
    
    shell> ndb_import myndb /tmp/myndb_table.csv --fields-optionally-enclosed-by='"' \
        --fields-terminated-by="," --fields-escaped-by='\\'
    

    The output should resemble what is shown here:

    job-1 import myndb.myndb_table from /tmp/myndb_table.csv
    job-1 [running] import myndb.myndb_table from /tmp/myndb_table.csv
    job-1 [success] import myndb.myndb_table from /tmp/myndb_table.csv
    job-1 imported 19984 rows in 0h0m9s at 2277 rows/s
    jobs summary: defined: 1 run: 1 with success: 1 with failure: 0
    shell>
    

The following table includes options that are specific to ndb_import. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_import), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.35 Command-line options for the ndb_import program

Format Description Added, Deprecated, or Removed

--abort-on-error

Dump core on any fatal error; used for debugging

(Supported in all MySQL 8.0 based releases)

--ai-increment=#

For table with hidden PK, specify autoincrement increment. See mysqld

(Supported in all MySQL 8.0 based releases)

--ai-offset=#

For table with hidden PK, specify autoincrement offset. See mysqld

(Supported in all MySQL 8.0 based releases)

--ai-prefetch-sz=#

For table with hidden PK, specify number of autoincrement values that are prefetched. See mysqld

(Supported in all MySQL 8.0 based releases)

--connections=#

Number of cluster connections to create

(Supported in all MySQL 8.0 based releases)

--continue

When job fails, continue to next job

(Supported in all MySQL 8.0 based releases)

--db-workers=#

Number of threads, per data node, executing database operations

(Supported in all MySQL 8.0 based releases)

--errins-type=name

Error insert type, for testing purposes; use "list" to obtain all possible values

(Supported in all MySQL 8.0 based releases)

--errins-delay=#

Error insert delay in milliseconds; random variation is added

(Supported in all MySQL 8.0 based releases)

--fields-enclosed-by=char

Same as FIELDS ENCLOSED BY option for LOAD DATA statements. For CSV input this is same as using --fields-optionally-enclosed-by

(Supported in all MySQL 8.0 based releases)

--fields-escaped-by=name

Same as FIELDS ESCAPED BY option for LOAD DATA statements

(Supported in all MySQL 8.0 based releases)

--fields-optionally-enclosed-by=char

Same as FIELDS OPTIONALLY ENCLOSED BY option for LOAD DATA statements

(Supported in all MySQL 8.0 based releases)

--fields-terminated-by=char

Same as FIELDS TERMINATED BY option for LOAD DATA statements

(Supported in all MySQL 8.0 based releases)

--idlesleep=#

Number of milliseconds to sleep waiting for more to do

(Supported in all MySQL 8.0 based releases)

--idlespin=#

Number of times to re-try before idlesleep

(Supported in all MySQL 8.0 based releases)

--ignore-lines=#

Ignore first # lines in input file. Used to skip a non-data header

(Supported in all MySQL 8.0 based releases)

--input-type=name

Input type: random or csv

(Supported in all MySQL 8.0 based releases)

--input-workers=#

Number of threads processing input. Must be 2 or more if --input-type is csv

(Supported in all MySQL 8.0 based releases)

--keep-state

State files (except non-empty *.rej files) are normally removed on job completion. Using this option causes all state files to be preserved instead

(Supported in all MySQL 8.0 based releases)

--lines-terminated-by=name

Same as LINES TERMINATED BY option for LOAD DATA statements

(Supported in all MySQL 8.0 based releases)

--max-rows=#

Import only this number of input data rows; default is 0, which imports all rows

(Supported in all MySQL 8.0 based releases)

--monitor=#

Periodically print status of running job if something has changed (status, rejected rows, temporary errors). Value 0 disables. Value 1 prints any change seen. Higher values reduce status printing exponentially up to some pre-defined limit

(Supported in all MySQL 8.0 based releases)

--no-asynch

Run database operations as batches, in single transactions

(Supported in all MySQL 8.0 based releases)

--no-hint

Do not use distribution key hint to select data node (TC)

(Supported in all MySQL 8.0 based releases)

--opbatch=#

A db execution batch is a set of transactions and operations sent to NDB kernel. This option limits NDB operations (including blob operations) in a db execution batch. Therefore it also limits number of asynch transactions. Value 0 is not valid

(Supported in all MySQL 8.0 based releases)

--opbytes=#

Limit bytes in execution batch (default 0 = no limit)

(Supported in all MySQL 8.0 based releases)

--output-type=name

Output type: ndb is default, null used for testing

(Supported in all MySQL 8.0 based releases)

--output-workers=#

Number of threads processing output or relaying database operations

(Supported in all MySQL 8.0 based releases)

--pagesize=#

Align I/O buffers to given size

(Supported in all MySQL 8.0 based releases)

--pagecnt=#

Size of I/O buffers as multiple of page size. CSV input worker allocates a double-sized buffer

(Supported in all MySQL 8.0 based releases)

--polltimeout=#

Timeout per poll for completed asynchonous transactions; polling continues until all polls are completed, or error occurs

(Supported in all MySQL 8.0 based releases)

--rejects=#

Limit number of rejected rows (rows with permanent error) in data load. Default is 0 which means that any rejected row causes a fatal error. The row exceeding the limit is also added to *.rej

(Supported in all MySQL 8.0 based releases)

--resume

If job aborted (temporary error, user interrupt), resume with rows not yet processed

(Supported in all MySQL 8.0 based releases)

--rowbatch=#

Limit rows in row queues (default 0 = no limit); must be 1 or more if --input-type is random

(Supported in all MySQL 8.0 based releases)

--rowbytes=#

Limit bytes in row queues (0 = no limit)

(Supported in all MySQL 8.0 based releases)

--state-dir=name

Where to write state files; currect directory is default

(Supported in all MySQL 8.0 based releases)

--stats

Save performance related options and internal statistics in *.sto and *.stt files. These files are kept on successful completion even if --keep-state is not used

(Supported in all MySQL 8.0 based releases)

--tempdelay=#

Number of milliseconds to sleep between temporary errors

(Supported in all MySQL 8.0 based releases)

--temperrors=#

Number of times a transaction can fail due to a temporary error, per execution batch; 0 means any temporary error is fatal. Such errors do not cause any rows to be written to .rej file

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Enable verbose output

(Supported in all MySQL 8.0 based releases)


  • --abort-on-error

    Command-Line Format --abort-on-error
    Type Boolean
    Default Value FALSE

    Dump core on any fatal error; used for debugging only.

  • --ai-increment=#

    Command-Line Format --ai-increment=#
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 4294967295

    For a table with a hidden primary key, specify the autoincrement increment, like the auto_increment_increment system variable does in the MySQL Server.

  • --ai-offset=#

    Command-Line Format --ai-offset=#
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 4294967295

    For a table with hidden primary key, specify the autoincrement offset. Similar to the auto_increment_offset system variable.

  • --ai-prefetch-sz=#

    Command-Line Format --ai-prefetch-sz=#
    Type Integer
    Default Value 1024
    Minimum Value 1
    Maximum Value 4294967295

    For a table with a hidden primary key, specify the number of autoincrement values that are prefetched. Behaves like the ndb_autoincrement_prefetch_sz system variable does in the MySQL Server.

  • --connections=#

    Command-Line Format --connections=#
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 4294967295

    Number of cluster connections to create.

  • --continue

    Command-Line Format --continue
    Type Boolean
    Default Value FALSE

    When a job fails, continue to the next job.

  • --db-workers=#

    Command-Line Format --db-workers=#
    Type Integer
    Default Value 4
    Minimum Value 1
    Maximum Value 4294967295

    Number of threads, per data node, executing database operations.

  • --errins-type=name

    Command-Line Format --errins-type=name
    Type Enumeration
    Default Value [none]
    Valid Values

    stopjob

    stopall

    sighup

    sigint

    list

    Error insert type; use list as the name value to obtain all possible values. This option is used for testing purposes only.

  • --errins-delay=#

    Command-Line Format --errins-delay=#
    Type Integer
    Default Value 1000
    Minimum Value 0
    Maximum Value 4294967295
    Unit ms

    Error insert delay in milliseconds; random variation is added. This option is used for testing purposes only.

  • --fields-enclosed-by=char

    Command-Line Format --fields-enclosed-by=char
    Type String
    Default Value [none]

    This works in the same way as the FIELDS ENCLOSED BY option does for the LOAD DATA statement, specifying a character to be interpeted as quoting field values. For CSV input, this is the same as --fields-optionally-enclosed-by.

  • --fields-escaped-by=name

    Command-Line Format --fields-escaped-by=name
    Type String
    Default Value \

    Specify an escape character in the same way as the FIELDS ESCAPED BY option does for the SQL LOAD DATA statement.

  • --fields-optionally-enclosed-by=char

    Command-Line Format --fields-optionally-enclosed-by=char
    Type String
    Default Value [none]

    This works in the same way as the FIELDS OPTIONALLY ENCLOSED BY option does for the LOAD DATA statement, specifying a character to be interpeted as optionally quoting field values. For CSV input, this is the same as --fields-enclosed-by.

  • --fields-terminated-by=char

    Command-Line Format --fields-terminated-by=char
    Type String
    Default Value \t

    This works in the same way as the FIELDS TERMINATED BY option does for the LOAD DATA statement, specifying a character to be interpeted as the field separator.

  • --idlesleep=#

    Command-Line Format --idlesleep=#
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 4294967295
    Unit ms

    Number of milliseconds to sleep waiting for more work to perform.

  • --idlespin=#

    Command-Line Format --idlespin=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Number of times to retry before sleeping.

  • --ignore-lines=#

    Command-Line Format --ignore-lines=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Cause ndb_import to ignore the first # lines of the input file. This can be employed to skip a file header that does not contain any data.

  • --input-type=name

    Command-Line Format --input-type=name
    Type Enumeration
    Default Value csv
    Valid Values

    random

    csv

    Set the type of input type. The default is csv; random is intended for testing purposes only. .

  • --input-workers=#

    Command-Line Format --input-workers=#
    Type Integer
    Default Value 4
    Minimum Value 1
    Maximum Value 4294967295

    Set the number of threads processing input.

  • --keep-state

    Command-Line Format --keep-state
    Type Boolean
    Default Value false

    By default, ndb_import removes all state files (except non-empty *.rej files) when it completes a job. Specify this option (nor argument is required) to force the program to retain all state files instead.

  • --lines-terminated-by=name

    Command-Line Format --lines-terminated-by=name
    Type String
    Default Value \n

    This works in the same way as the LINES TERMINATED BY option does for the LOAD DATA statement, specifying a character to be interpeted as end-of-line.

  • --log-level=#

    Command-Line Format --log-level=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 2

    Performs internal logging at the given level. This option is intended primarily for internal and development use.

    In debug builds of NDB only, the logging level can be set using this option to a maximum of 4.

  • --max-rows=#

    Command-Line Format --max-rows=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295
    Unit bytes

    Import only this number of input data rows; the default is 0, which imports all rows.

  • --monitor=#

    Command-Line Format --monitor=#
    Type Integer
    Default Value 2
    Minimum Value 0
    Maximum Value 4294967295
    Unit bytes

    Periodically print the status of a running job if something has changed (status, rejected rows, temporary errors). Set to 0 to disable this reporting. Setting to 1 prints any change that is seen. Higher values reduce the frequency of this status reporting.

  • --no-asynch

    Command-Line Format --no-asynch
    Type Boolean
    Default Value FALSE

    Run database operations as batches, in single transactions.

  • --no-hint

    Command-Line Format --no-hint
    Type Boolean
    Default Value FALSE

    Do not use distribution key hinting to select a data node.

  • --opbatch=#

    Command-Line Format --opbatch=#
    Type Integer
    Default Value 256
    Minimum Value 1
    Maximum Value 4294967295
    Unit bytes

    Set a limit on the number of operations (including blob operations), and thus the number of asynchronous transactions, per execution batch.

  • --opbytes=#

    Command-Line Format --opbytes=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295
    Unit bytes

    Set a limit on the number of bytes per execution batch. Use 0 for no limit.

  • --output-type=name

    Command-Line Format --output-type=name
    Type Enumeration
    Default Value ndb
    Valid Values null

    Set the output type. ndb is the default. null is used only for testing.

  • --output-workers=#

    Command-Line Format --output-workers=#
    Type Integer
    Default Value 2
    Minimum Value 1
    Maximum Value 4294967295

    Set the number of threads processing output or relaying database operations.

  • --pagesize=#

    Command-Line Format --pagesize=#
    Type Integer
    Default Value 4096
    Minimum Value 1
    Maximum Value 4294967295
    Unit bytes

    Align I/O buffers to the given size.

  • --pagecnt=#

    Command-Line Format --pagecnt=#
    Type Integer
    Default Value 64
    Minimum Value 1
    Maximum Value 4294967295

    Set the size of I/O buffers as multiple of page size. The CSV input worker allocates buffer that is doubled in size.

  • --polltimeout=#

    Command-Line Format --polltimeout=#
    Type Integer
    Default Value 1000
    Minimum Value 1
    Maximum Value 4294967295
    Unit ms

    Set a timeout per poll for completed asynchonous transactions; polling continues until all polls are completed, or until an error occurs.

  • --rejects=#

    Command-Line Format --rejects=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Limit the number of rejected rows (rows with permanent errors) in the data load. The default is 0, which means that any rejected row causes a fatal error. Any rows causing the limit to be exceeded are added to the .rej file.

    The limit imposed by this option is effective for the duration of the current run. A run restarted using --resume is considered a new run for this purpose.

  • --resume

    Command-Line Format --resume
    Type Boolean
    Default Value FALSE

    If a job is aborted (due to a temporary db error or when interrupted by the user), resume with any rows not yet processed.

  • --rowbatch=#

    Command-Line Format --rowbatch=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295
    Unit rows

    Set a limit on the number of rows per row queue. Use 0 for no limit.

  • --rowbytes=#

    Command-Line Format --rowbytes=#
    Type Integer
    Default Value 262144
    Minimum Value 0
    Maximum Value 4294967295
    Unit bytes

    Set a limit on the number of bytes per row queue. Use 0 for no limit.

  • --stats

    Command-Line Format --stats
    Type Boolean
    Default Value false

    Save information about options related to performance and other internal statistics in files named *.sto and *.stt. These files are always kept on successful completion (even if --keep-state is not also specified).

  • --state-dir=name

    Command-Line Format --state-dir=name
    Type String
    Default Value .

    Where to write the state files (tbl_name.map, tbl_name.rej, tbl_name.res, and tbl_name.stt) produced by a run of the program; the default is the current directory.

  • --tempdelay=#

    Command-Line Format --tempdelay=#
    Type Integer
    Default Value 10
    Minimum Value 0
    Maximum Value 4294967295
    Unit ms

    Number of milliseconds to sleep between temporary errors.

  • --temperrors=#

    Command-Line Format --temperrors=#
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 4294967295

    Number of times a transaction can fail due to a temporary error, per execution batch. The default is 0, which means that any temporary error is fatal. Temporary errors do not cause any rows to be added to the .rej file.

  • --verbose, -v

    Command-Line Format --verbose
    Type Boolean
    Default Value false

    Enable verbose output.

As with LOAD DATA, options for field and line formatting much match those used to create the CSV file, whether this was done using SELECT INTO ... OUTFILE, or by some other means. There is no equivalent to the LOAD DATA statement STARTING WITH option.

ndb_import was added in NDB 7.6.2.

23.4.14 ndb_index_stat — NDB Index Statistics Utility

ndb_index_stat provides per-fragment statistical information about indexes on NDB tables. This includes cache version and age, number of index entries per partition, and memory consumption by indexes.

Usage

To obtain basic index statistics about a given NDB table, invoke ndb_index_stat as shown here, with the name of the table as the first argument and the name of the database containing this table specified immediately following it, using the --database (-d) option:

ndb_index_stat table -d database

In this example, we use ndb_index_stat to obtain such information about an NDB table named mytable in the test database:

shell> ndb_index_stat -d test mytable
table:City index:PRIMARY fragCount:2
sampleVersion:3 loadTime:1399585986 sampleCount:1994 keyBytes:7976
query cache: valid:1 sampleCount:1994 totalBytes:27916
times in ms: save: 7.133 sort: 1.974 sort per sample: 0.000

NDBT_ProgramExit: 0 - OK

sampleVersion is the version number of the cache from which the statistics data is taken. Running ndb_index_stat with the --update option causes sampleVersion to be incremented.

loadTime shows when the cache was last updated. This is expressed as seconds since the Unix Epoch.

sampleCount is the number of index entries found per partition. You can estimate the total number of entries by multiplying this by the number of fragments (shown as fragCount).

sampleCount can be compared with the cardinality of SHOW INDEX or INFORMATION_SCHEMA.STATISTICS, although the latter two provide a view of the table as a whole, while ndb_index_stat provides a per-fragment average.

keyBytes is the number of bytes used by the index. In this example, the primary key is an integer, which requires four bytes for each index, so keyBytes can be calculated in this case as shown here:

    keyBytes = sampleCount * (4 bytes per index) = 1994 * 4 = 7976

This information can also be obtained using the corresponding column definitions from INFORMATION_SCHEMA.COLUMNS (this requires a MySQL Server and a MySQL client application).

totalBytes is the total memory consumed by all indexes on the table, in bytes.

Timings shown in the preceding examples are specific to each invocation of ndb_index_stat.

The --verbose option provides some additional output, as shown here:

shell> ndb_index_stat -d test mytable --verbose
random seed 1337010518
connected
loop 1 of 1
table:mytable index:PRIMARY fragCount:4
sampleVersion:2 loadTime:1336751773 sampleCount:0 keyBytes:0
read stats
query cache created
query cache: valid:1 sampleCount:0 totalBytes:0
times in ms: save: 20.766 sort: 0.001
disconnected

NDBT_ProgramExit: 0 - OK

shell>

If the only output from the program is NDBT_ProgramExit: 0 - OK, this may indicate that no statistics yet exist. To force them to be created (or updated if they already exist), invoke ndb_index_stat with the --update option, or execute ANALYZE TABLE on the table in the mysql client.

Options

The following table includes options that are specific to the NDB Cluster ndb_index_stat utility. Additional descriptions are listed following the table. For options common to most NDB Cluster programs (including ndb_index_stat), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.36 Command-line options for the ndb_index_stat program

Format Description Added, Deprecated, or Removed

--database=name,

-d

Name of database containing table

(Supported in all MySQL 8.0 based releases)

--delete

Delete index statistics for table, stopping any auto-update previously configured

(Supported in all MySQL 8.0 based releases)

--update

Update index statistics for table, restarting any auto-update previously configured

(Supported in all MySQL 8.0 based releases)

--dump

Print query cache

(Supported in all MySQL 8.0 based releases)

--query=#

Perform random range queries on first key attr (must be int unsigned)

(Supported in all MySQL 8.0 based releases)

--sys-drop

Drop any statistics tables and events in NDB kernel (all statistics are lost)

(Supported in all MySQL 8.0 based releases)

--sys-create

Create all statistics tables and events in NDB kernel, if none of them already exist

(Supported in all MySQL 8.0 based releases)

--sys-create-if-not-exist

Create any statistics tables and events in NDB kernel that do not already exist

(Supported in all MySQL 8.0 based releases)

--sys-create-if-not-valid

Create any statistics tables or events that do not already exist in the NDB kernel, after dropping any that are invalid

(Supported in all MySQL 8.0 based releases)

--sys-check

Verify that NDB system index statistics and event tables exist

(Supported in all MySQL 8.0 based releases)

--sys-skip-tables

Do not apply sys-* options to tables

(Supported in all MySQL 8.0 based releases)

--sys-skip-events

Do not apply sys-* options to events

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Turn on verbose output

(Supported in all MySQL 8.0 based releases)

--loops=#

Set the number of times to perform given command; default is 0

(Supported in all MySQL 8.0 based releases)


ndb_index_stat statistics options.  The following options are used to generate index statistics. They work with a given table and database. They cannot be mixed with system options (see ndb_index_stat system options).

  • --database=name, -d name

    Command-Line Format --database=name
    Type String
    Default Value [none]
    Minimum Value
    Maximum Value

    The name of the database that contains the table being queried.

  • --delete

    Command-Line Format --delete
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Delete the index statistics for the given table, stopping any auto-update that was previously configured.

  • --update

    Command-Line Format --update
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Update the index statistics for the given table, and restart any auto-update that was previously configured.

  • --dump

    Command-Line Format --dump
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Dump the contents of the query cache.

  • --query=#

    Command-Line Format --query=#
    Type Numeric
    Default Value 0
    Minimum Value 0
    Maximum Value MAX_INT

    Perform random range queries on first key attribute (must be int unsigned).

ndb_index_stat system options.  The following options are used to generate and update the statistics tables in the NDB kernel. None of these options can be mixed with statistics options (see ndb_index_stat statistics options).

  • --sys-drop

    Command-Line Format --sys-drop
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Drop all statistics tables and events in the NDB kernel. This causes all statistics to be lost.

  • --sys-create

    Command-Line Format --sys-create
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Create all statistics tables and events in the NDB kernel. This works only if none of them exist previously.

  • sys-create-if-not-exist

    Command-Line Format --sys-create-if-not-exist
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Create any NDB system statistics tables or events (or both) that do not already exist when the program is invoked.

  • --sys-create-if-not-valid

    Command-Line Format --sys-create-if-not-valid
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Create any NDB system statistics tables or events that do not already exist, after dropping any that are invalid.

  • --sys-check

    Command-Line Format --sys-check
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Verify that all required system statistics tables and events exist in the NDB kernel.

  • --sys-skip-tables

    Command-Line Format --sys-skip-tables
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Do not apply any --sys-* options to any statistics tables.

  • --sys-skip-events

    Command-Line Format --sys-skip-events
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Do not apply any --sys-* options to any events.

  • --verbose

    Command-Line Format --verbose
    Type Boolean
    Default Value false
    Minimum Value
    Maximum Value

    Turn on verbose output.

  • --loops=#

    Command-Line Format --loops=#
    Type Numeric
    Default Value 0
    Minimum Value 0
    Maximum Value MAX_INT

    Repeat commands this number of times (for use in testing).

23.4.15 ndb_move_data — NDB Data Copy Utility

ndb_move_data copies data from one NDB table to another.

Usage

The program is invoked with the names of the source and target tables; either or both of these may be qualified optionally with the database name. Both tables must use the NDB storage engine.

ndb_move_data options source target

The following table includes options that are specific to ndb_move_data. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_move_data), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.37 Command-line options for the ndb_move_data program

Format Description Added, Deprecated, or Removed

--abort-on-error

Dump core on permanent error (debug option)

(Supported in all MySQL 8.0 based releases)

--character-sets-dir=name

Directory where character sets are

(Supported in all MySQL 8.0 based releases)

--database=dbname,

-d

Name of database in which table is found

(Supported in all MySQL 8.0 based releases)

--drop-source

Drop source table after all rows have been moved

(Supported in all MySQL 8.0 based releases)

--error-insert

Insert random temporary errors (testing option)

(Supported in all MySQL 8.0 based releases)

--exclude-missing-columns

Ignore extra columns in source or target table

(Supported in all MySQL 8.0 based releases)

--lossy-conversions,

-l

Allow attribute data to be truncated when converted to smaller type

(Supported in all MySQL 8.0 based releases)

--promote-attributes,

-A

Allow attribute data to be converted to larger type

(Supported in all MySQL 8.0 based releases)

--staging-tries=x[,y[,z]]

Specify tries on temporary errors; format is x[,y[,z]] where x=max tries (0=no limit), y=min delay (ms), z=max delay (ms)

(Supported in all MySQL 8.0 based releases)

--verbose

Enable verbose messages

(Supported in all MySQL 8.0 based releases)


  • --abort-on-error

    Command-Line Format --abort-on-error
    Type Boolean
    Default Value FALSE

    Dump core on permanent error (debug option).

  • --character-sets-dir=name

    Command-Line Format --character-sets-dir=name
    Type String
    Default Value [none]

    Directory where character sets are.

  • --database=dbname, -d

    Command-Line Format --database=dbname
    Type String
    Default Value TEST_DB

    Name of the database in which the table is found.

  • --drop-source

    Command-Line Format --drop-source
    Type Boolean
    Default Value FALSE

    Drop source table after all rows have been moved.

  • --error-insert

    Command-Line Format --error-insert
    Type Boolean
    Default Value FALSE

    Insert random temporary errors (testing option).

  • --exclude-missing-columns

    Command-Line Format --exclude-missing-columns
    Type Boolean
    Default Value FALSE

    Ignore extra columns in source or target table.

  • --lossy-conversions, -l

    Command-Line Format --lossy-conversions
    Type Boolean
    Default Value FALSE

    Allow attribute data to be truncated when converted to a smaller type.

  • --promote-attributes, -A

    Command-Line Format --promote-attributes
    Type Boolean
    Default Value FALSE

    Allow attribute data to be converted to a larger type.

  • --staging-tries=x[,y[,z]]

    Command-Line Format --staging-tries=x[,y[,z]]
    Type String
    Default Value 0,1000,60000

    Specify tries on temporary errors. Format is x[,y[,z]] where x=max tries (0=no limit), y=min delay (ms), z=max delay (ms).

  • --verbose

    Command-Line Format --verbose
    Type Boolean
    Default Value FALSE

    Enable verbose messages.

23.4.16 ndb_perror — Obtain NDB Error Message Information

ndb_perror shows information about an NDB error, given its error code. This includes the error message, the type of error, and whether the error is permanent or temporary. Added to the MySQL NDB Cluster distribution in NDB 7.6.4, it is intended as a drop-in replacement for perror --ndb.

Usage

ndb_perror [options] error_code

ndb_perror does not need to access a running NDB Cluster, or any nodes (including SQL nodes). To view information about a given NDB error, invoke the program, using the error code as an argument, like this:

shell> ndb_perror 323
NDB error code 323: Invalid nodegroup id, nodegroup already existing: Permanent error: Application error

To display only the error message, invoke ndb_perror with the --silent option (short form -s), as shown here:

shell> ndb_perror -s 323
Invalid nodegroup id, nodegroup already existing: Permanent error: Application error

Like perror, ndb_perror accepts multiple error codes:

shell> ndb_perror 321 1001
NDB error code 321: Invalid nodegroup id: Permanent error: Application error
NDB error code 1001: Illegal connect string

Additional program options for ndb_perror are described later in this section.

ndb_perror replaces perror --ndb, which is deprecated as of NDB 7.6.4 and subject to removal in a future release of MySQL NDB Cluster. To make substitution easier in scripts and other applications that might depend on perror for obtaining NDB error information, ndb_perror supports its own dummy --ndb option, which does nothing.

The following table includes all options that are specific to the NDB Cluster program ndb_perror. Additional descriptions follow the table.

Table 23.38 Command-line options for the ndb_perror program

Format Description Added, Deprecated, or Removed

--help,

-?

Display help text

(Supported in all MySQL 8.0 based releases)

--ndb

For compatibility with applications depending on old versions of perror; does nothing

(Supported in all MySQL 8.0 based releases)

--silent,

-s

Show error message only

(Supported in all MySQL 8.0 based releases)

--version,

-V

Print program version information and exit

(Supported in all MySQL 8.0 based releases)

--verbose,

-v

Verbose output; disable with --silent

(Supported in all MySQL 8.0 based releases)


Additional Options

  • --help, -?

    Command-Line Format --help
    Type Boolean
    Default Value TRUE

    Display program help text and exit.

  • --ndb

    Command-Line Format --ndb
    Type Boolean
    Default Value TRUE

    For compatibility with applications depending on old versions of perror that use that program's --ndb option. The option when used with ndb_perror does nothing, and is ignored by it.

  • --silent, -s

    Command-Line Format --silent
    Type Boolean
    Default Value TRUE

    Show error message only.

  • --version, -V

    Command-Line Format --version
    Type Boolean
    Default Value TRUE

    Print program version information and exit.

  • --verbose, -v

    Command-Line Format --verbose
    Type Boolean
    Default Value TRUE

    Verbose output; disable with --silent.

23.4.17 ndb_print_backup_file — Print NDB Backup File Contents

ndb_print_backup_file obtains diagnostic information from a cluster backup file.

Usage

ndb_print_backup_file [-P password] file_name

file_name is the name of a cluster backup file. This can be any of the files (.Data, .ctl, or .log file) found in a cluster backup directory. These files are found in the data node's backup directory under the subdirectory BACKUP-#, where # is the sequence number for the backup. For more information about cluster backup files and their contents, see Section 23.5.8.1, “NDB Cluster Backup Concepts”.

Like ndb_print_schema_file and ndb_print_sys_file (and unlike most of the other NDB utilities that are intended to be run on a management server host or to connect to a management server) ndb_print_backup_file must be run on a cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

In NDB 8.0.17 and later, this program can also be used to read undo log files.

Beginning with NDB 8.0.22, this program can read encrypted backups. To do this, supply the -P option together with the password used to encrypt the backup.

Additional Options

None.

23.4.18 ndb_print_file — Print NDB Disk Data File Contents

ndb_print_file obtains information from an NDB Cluster Disk Data file.

Usage

ndb_print_file [-v] [-q] file_name+

file_name is the name of an NDB Cluster Disk Data file. Multiple filenames are accepted, separated by spaces.

Like ndb_print_schema_file and ndb_print_sys_file (and unlike most of the other NDB utilities that are intended to be run on a management server host or to connect to a management server) ndb_print_file must be run on an NDB Cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

Additional Options

ndb_print_file supports the following options:

  • -v: Make output verbose.

  • -q: Suppress output (quiet mode).

  • --help, -h, -?: Print help message.

For more information, see Section 23.5.10, “NDB Cluster Disk Data Tables”.

23.4.19 ndb_print_frag_file — Print NDB Fragment List File Contents

ndb_print_frag_file obtains information from a cluster fragment list file. It is intended for use in helping to diagnose issues with data node restarts.

Usage

ndb_print_frag_file file_name

file_name is the name of a cluster fragment list file, which matches the pattern SX.FragList, where X is a digit in the range 2-9 inclusive, and are found in the data node file system of the data node having the node ID nodeid, in directories named ndb_nodeid_fs/DN/DBDIH/, where N is 1 or 2. Each fragment file contains records of the fragments belonging to each NDB table. For more information about cluster fragment files, see NDB Cluster Data Node File System Directory.

Like ndb_print_backup_file, ndb_print_sys_file, and ndb_print_schema_file (and unlike most of the other NDB utilities that are intended to be run on a management server host or to connect to a management server), ndb_print_frag_file must be run on a cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

Additional Options

None.

Sample Output

shell> ndb_print_frag_file /usr/local/mysqld/data/ndb_3_fs/D1/DBDIH/S2.FragList
Filename: /usr/local/mysqld/data/ndb_3_fs/D1/DBDIH/S2.FragList with size 8192
noOfPages = 1 noOfWords = 182
Table Data
----------
Num Frags: 2 NoOfReplicas: 2 hashpointer: 4294967040
kvalue: 6 mask: 0x00000000 method: HashMap
Storage is on Logged and checkpointed, survives SR
------ Fragment with FragId: 0 --------
Preferred Primary: 2 numStoredReplicas: 2 numOldStoredReplicas: 0 distKey: 0 LogPartId: 0
-------Stored Replica----------
Replica node is: 2 initialGci: 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo[0]: maxGciCompleted: 1 maxGciStarted: 2 lcpId: 1 lcpStatus: valid
LcpNo[1]: maxGciCompleted: 0 maxGciStarted: 0 lcpId: 0 lcpStatus: invalid
-------Stored Replica----------
Replica node is: 3 initialGci: 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo[0]: maxGciCompleted: 1 maxGciStarted: 2 lcpId: 1 lcpStatus: valid
LcpNo[1]: maxGciCompleted: 0 maxGciStarted: 0 lcpId: 0 lcpStatus: invalid
------ Fragment with FragId: 1 --------
Preferred Primary: 3 numStoredReplicas: 2 numOldStoredReplicas: 0 distKey: 0 LogPartId: 1
-------Stored Replica----------
Replica node is: 3 initialGci: 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo[0]: maxGciCompleted: 1 maxGciStarted: 2 lcpId: 1 lcpStatus: valid
LcpNo[1]: maxGciCompleted: 0 maxGciStarted: 0 lcpId: 0 lcpStatus: invalid
-------Stored Replica----------
Replica node is: 2 initialGci: 2 numCrashedReplicas = 0 nextLcpNo = 1
LcpNo[0]: maxGciCompleted: 1 maxGciStarted: 2 lcpId: 1 lcpStatus: valid
LcpNo[1]: maxGciCompleted: 0 maxGciStarted: 0 lcpId: 0 lcpStatus: invalid

23.4.20 ndb_print_schema_file — Print NDB Schema File Contents

ndb_print_schema_file obtains diagnostic information from a cluster schema file.

Usage

ndb_print_schema_file file_name

file_name is the name of a cluster schema file. For more information about cluster schema files, see NDB Cluster Data Node File System Directory.

Like ndb_print_backup_file and ndb_print_sys_file (and unlike most of the other NDB utilities that are intended to be run on a management server host or to connect to a management server) ndb_print_schema_file must be run on a cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

Additional Options

None.

23.4.21 ndb_print_sys_file — Print NDB System File Contents

ndb_print_sys_file obtains diagnostic information from an NDB Cluster system file.

Usage

ndb_print_sys_file file_name

file_name is the name of a cluster system file (sysfile). Cluster system files are located in a data node's data directory (DataDir); the path under this directory to system files matches the pattern ndb_#_fs/D#/DBDIH/P#.sysfile. In each case, the # represents a number (not necessarily the same number). For more information, see NDB Cluster Data Node File System Directory.

Like ndb_print_backup_file and ndb_print_schema_file (and unlike most of the other NDB utilities that are intended to be run on a management server host or to connect to a management server) ndb_print_backup_file must be run on a cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

Additional Options

None.

23.4.22 ndb_redo_log_reader — Check and Print Content of Cluster Redo Log

Reads a redo log file, checking it for errors, printing its contents in a human-readable format, or both. ndb_redo_log_reader is intended for use primarily by NDB Cluster developers and Support personnel in debugging and diagnosing problems.

This utility remains under development, and its syntax and behavior are subject to change in future NDB Cluster releases.

The C++ source files for ndb_redo_log_reader can be found in the directory /storage/ndb/src/kernel/blocks/dblqh/redoLogReader.

The following table includes options that are specific to the NDB Cluster program ndb_redo_log_reader. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_redo_log_reader), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.39 Command-line options for the ndb_redo_log_reader program

Format Description Added, Deprecated, or Removed

-dump

Print dump info

(Supported in all MySQL 8.0 based releases)

-filedescriptors

Print file descriptors only

(Supported in all MySQL 8.0 based releases)

--help

Print usage information

(Supported in all MySQL 8.0 based releases)

-lap

Provide lap info, with max GCI started and completed

(Supported in all MySQL 8.0 based releases)

-mbyte #

Starting megabyte

(Supported in all MySQL 8.0 based releases)

-mbyteheaders

Show only first page header of each megabyte in file

(Supported in all MySQL 8.0 based releases)

-nocheck

Do not check records for errors

(Supported in all MySQL 8.0 based releases)

-noprint

Do not print records

(Supported in all MySQL 8.0 based releases)

-page #

Start with this page

(Supported in all MySQL 8.0 based releases)

-pageheaders

Show page headers only

(Supported in all MySQL 8.0 based releases)

-pageindex #

Start with this page index

(Supported in all MySQL 8.0 based releases)

-twiddle

Bit-shifted dump

(Supported in all MySQL 8.0 based releases)


Usage

ndb_redo_log_reader file_name [options]

file_name is the name of a cluster redo log file. redo log files are located in the numbered directories under the data node's data directory (DataDir); the path under this directory to the redo log files matches the pattern ndb_nodeid_fs/D#/DBLQH/S#.FragLog. nodeid is the data node's node ID. The two instances of # each represent a number (not necessarily the same number); the number following D is in the range 8-39 inclusive; the range of the number following S varies according to the value of the NoOfFragmentLogFiles configuration parameter, whose default value is 16; thus, the default range of the number in the file name is 0-15 inclusive. For more information, see NDB Cluster Data Node File System Directory.

The name of the file to be read may be followed by one or more of the options listed here:

  • -dump

    Command-Line Format -dump
    Type Boolean
    Default Value FALSE

    Print dump info.

  • Command-Line Format -filedescriptors
    Type Boolean
    Default Value FALSE

    -filedescriptors: Print file descriptors only.

  • Command-Line Format --help

    --help: Print usage information.

  • -lap

    Command-Line Format -lap
    Type Boolean
    Default Value FALSE

    Provide lap info, with max GCI started and completed.

  • Command-Line Format -mbyte #
    Type Numeric
    Default Value 0
    Minimum Value 0
    Maximum Value 15

    -mbyte #: Starting megabyte.

    # is an integer in the range 0 to 15, inclusive.

  • Command-Line Format -mbyteheaders
    Type Boolean
    Default Value FALSE

    -mbyteheaders: Show only the first page header of every megabyte in the file.

  • Command-Line Format -noprint
    Type Boolean
    Default Value FALSE

    -noprint: Do not print the contents of the log file.

  • Command-Line Format -nocheck
    Type Boolean
    Default Value FALSE

    -nocheck: Do not check the log file for errors.

  • Command-Line Format -page #
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 31

    -page #: Start at this page.

    # is an integer in the range 0 to 31, inclusive.

  • Command-Line Format -pageheaders
    Type Boolean
    Default Value FALSE

    -pageheaders: Show page headers only.

  • Command-Line Format -pageindex #
    Type Integer
    Default Value 12
    Minimum Value 12
    Maximum Value 8191

    -pageindex #: Start at this page index.

    # is an integer between 12 and 8191, inclusive.

  • -twiddle

    Command-Line Format -twiddle
    Type Boolean
    Default Value FALSE

    Bit-shifted dump.

Like ndb_print_backup_file and ndb_print_schema_file (and unlike most of the NDB utilities that are intended to be run on a management server host or to connect to a management server) ndb_redo_log_reader must be run on a cluster data node, since it accesses the data node file system directly. Because it does not make use of the management server, this utility can be used when the management server is not running, and even when the cluster has been completely shut down.

23.4.23 ndb_restore — Restore an NDB Cluster Backup

The NDB Cluster restoration program is implemented as a separate command-line utility ndb_restore, which can normally be found in the MySQL bin directory. This program reads the files created as a result of the backup and inserts the stored information into the database.

Note

Beginning with NDB 8.0.17, this program no longer prints NDBT_ProgramExit: ... when it finishes its run. Applications depending on this behavior should be modified accordingly when upgrading from NDB 8.0.16 or earlier to a NDB 8.0 later release.

ndb_restore must be executed once for each of the backup files that were created by the START BACKUP command used to create the backup (see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”). This is equal to the number of data nodes in the cluster at the time that the backup was created.

Note

Before using ndb_restore, it is recommended that the cluster be running in single user mode, unless you are restoring multiple data nodes in parallel. See Section 23.5.6, “NDB Cluster Single User Mode”, for more information.

The following table includes options that are specific to the NDB Cluster native backup restoration program ndb_restore. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_restore), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.40 Command-line options for the ndb_restore program

Format Description Added, Deprecated, or Removed

--allow-pk-changes[=0|1]

Allow changes to set of columns making up table's primary key

ADDED: NDB 8.0.21

--append

Append data to tab-delimited file

(Supported in all MySQL 8.0 based releases)

--backup-password=string

Supply a password for decrypting an encrypted backup with --decrypt; see documentation for allowed values

ADDED: NDB 8.0.22

--backup-path=dir_name

Path to backup files directory

(Supported in all MySQL 8.0 based releases)

--backupid=#,

-b

Restore from backup having this ID

(Supported in all MySQL 8.0 based releases)

--connect,

-c

Alias for --connectstring

(Supported in all MySQL 8.0 based releases)

--decrypt

Decrypt an encrypted backup; requires --backup-password

ADDED: NDB 8.0.22

--disable-indexes

Causes indexes from backup to be ignored; may decrease time needed to restore data

(Supported in all MySQL 8.0 based releases)

--dont-ignore-systab-0,

-f

Do not ignore system table during restore; experimental only; not for production use

(Supported in all MySQL 8.0 based releases)

--exclude-databases=db-list

List of one or more databases to exclude (includes those not named)

(Supported in all MySQL 8.0 based releases)

--exclude-intermediate-sql-tables[=TRUE|FALSE]

If TRUE (default), do not restore any intermediate tables (having names prefixed with '#sql-') that were left over from copying ALTER TABLE operations

(Supported in all MySQL 8.0 based releases)

--exclude-missing-columns

Causes columns from backup version of table that are missing from version of table in database to be ignored

(Supported in all MySQL 8.0 based releases)

--exclude-missing-tables

Causes tables from backup that are missing from database to be ignored

(Supported in all MySQL 8.0 based releases)

--exclude-tables=table-list

List of one or more tables to exclude (includes those in same database that are not named); each table reference must include database name

(Supported in all MySQL 8.0 based releases)

--fields-enclosed-by=char

Fields are enclosed by this character

(Supported in all MySQL 8.0 based releases)

--fields-optionally-enclosed-by

Fields are optionally enclosed by this character

(Supported in all MySQL 8.0 based releases)

--fields-terminated-by=char

Fields are terminated by this character

(Supported in all MySQL 8.0 based releases)

--hex

Print binary types in hexadecimal format

(Supported in all MySQL 8.0 based releases)

--ignore-extended-pk-updates[=0|1]

Ignore log entries containing updates to columns now included in extended primary key

ADDED: NDB 8.0.21

--include-databases=db-list

List of one or more databases to restore (excludes those not named)

(Supported in all MySQL 8.0 based releases)

--include-stored-grants

Restore shared users and grants to ndb_sql_metadata table

ADDED: NDB 8.0.19

--include-tables=table-list

List of one or more tables to restore (excludes those in same database that are not named); each table reference must include database name

(Supported in all MySQL 8.0 based releases)

--lines-terminated-by=char

Lines are terminated by this character

(Supported in all MySQL 8.0 based releases)

--lossy-conversions,

-L

Allow lossy conversions of column values (type demotions or changes in sign) when restoring data from backup

(Supported in all MySQL 8.0 based releases)

--no-binlog

If mysqld is connected and using binary logging, do not log restored data

(Supported in all MySQL 8.0 based releases)

--no-restore-disk-objects,

-d

Do not restore objects relating to Disk Data

(Supported in all MySQL 8.0 based releases)

--no-upgrade,

-u

Do not upgrade array type for varsize attributes which do not already resize VAR data, and do not change column attributes

(Supported in all MySQL 8.0 based releases)

--ndb-nodegroup-map=map,

-z

Nodegroup map for NDBCLUSTER storage engine; syntax: list of (source_nodegroup, destination_nodegroup)

(Supported in all MySQL 8.0 based releases)

--nodeid=#,

-n

ID of node where backup was taken

(Supported in all MySQL 8.0 based releases)

--num-slices=#

Number of slices to apply when restoring by slice

ADDED: NDB 8.0.20

--parallelism=#,

-p

Number of parallel transactions to use while restoring data

(Supported in all MySQL 8.0 based releases)

--preserve-trailing-spaces,

-P

Allow preservation of trailing spaces (including padding) when promoting fixed-width string types to variable-width types

(Supported in all MySQL 8.0 based releases)

--print

Print metadata, data, and log to stdout (equivalent to --print-meta --print-data --print-log)

(Supported in all MySQL 8.0 based releases)

--print-data

Print data to stdout

(Supported in all MySQL 8.0 based releases)

--print-log

Print log to stdout

(Supported in all MySQL 8.0 based releases)

--print-meta

Print metadata to stdout

(Supported in all MySQL 8.0 based releases)

--print-sql-log

Write SQL log to stdout; default is FALSE

(Supported in all MySQL 8.0 based releases)

--progress-frequency=#

Print status of restore each given number of seconds

(Supported in all MySQL 8.0 based releases)

--promote-attributes,

-A

Allow attributes to be promoted when restoring data from backup

(Supported in all MySQL 8.0 based releases)

--rebuild-indexes

Causes multithreaded rebuilding of ordered indexes found in backup; number of threads used is determined by setting BuildIndexThreads

(Supported in all MySQL 8.0 based releases)

--remap-column=[db].[tbl].[col]:[fn]:[args]

Apply offset to value of specified column using indicated function and arguments

ADDED: NDB 8.0.21

--restore-data,

-r

Restore table data and logs into NDB Cluster using NDB API

(Supported in all MySQL 8.0 based releases)

--restore-epoch,

-e

Restore epoch info into status table; useful on replica cluster for starting replication; updates or inserts row in mysql.ndb_apply_status with ID 0

(Supported in all MySQL 8.0 based releases)

--restore-meta,

-m

Restore metadata to NDB Cluster using NDB API

(Supported in all MySQL 8.0 based releases)

--restore-privilege-tables

Restore MySQL privilege tables that were previously moved to NDB

DEPRECATED: NDB 8.0.16

--rewrite-database=olddb,newdb

Restore to differently named database

(Supported in all MySQL 8.0 based releases)

--skip-broken-objects

Ignore missing blob tables in backup file

(Supported in all MySQL 8.0 based releases)

--skip-table-check,

-s

Skip table structure check during restore

(Supported in all MySQL 8.0 based releases)

--skip-unknown-objects

Causes schema objects not recognized by ndb_restore to be ignored when restoring backup made from newer NDB version to older version

(Supported in all MySQL 8.0 based releases)

--slice-id=#

Slice ID, when restoring by slices

ADDED: NDB 8.0.20

--tab=dir_name,

-T dir_name

Creates a tab-separated .txt file for each table in path provided

(Supported in all MySQL 8.0 based releases)

--verbose=#

Level of verbosity in output

(Supported in all MySQL 8.0 based releases)


Typical options for this utility are shown here:

ndb_restore [-c connection_string] -n node_id -b backup_id \
      [-m] -r --backup-path=/path/to/backup/files

Normally, when restoring from an NDB Cluster backup, ndb_restore requires at a minimum the --nodeid (short form: -n), --backupid (short form: -b), and --backup-path options.

Prior to NDB 8.0.19, when ndb_restore was used to restore any tables containing unique indexes, it was necessary to include --disable-indexes or --rebuild-indexes. Beginning with NDB 8.0.19, when automatic metadata synchronization is enabled, this is no longer necessary.

The -c option is used to specify a connection string which tells ndb_restore where to locate the cluster management server (see Section 23.3.3.3, “NDB Cluster Connection Strings”). If this option is not used, then ndb_restore attempts to connect to a management server on localhost:1186. This utility acts as a cluster API node, and so requires a free connection slot to connect to the cluster management server. This means that there must be at least one [api] or [mysqld] section that can be used by it in the cluster config.ini file. It is a good idea to keep at least one empty [api] or [mysqld] section in config.ini that is not being used for a MySQL server or other application for this reason (see Section 23.3.3.7, “Defining SQL and Other API Nodes in an NDB Cluster”).

In NDB 8.0.22 and later, ndb_restore can decrypt an encrypted backup using --decrypt and --backup-password. Both options must be specified to perform decryption. See the documentation for the START BACKUP management client command for information on creating encrypted backups.

You can verify that ndb_restore is connected to the cluster by using the SHOW command in the ndb_mgm management client. You can also accomplish this from a system shell, as shown here:

shell> ndb_mgm -e "SHOW"

More detailed information about all options used by ndb_restore can be found in the following list:

  • --allow-pk-changes

    Command-Line Format --allow-pk-changes[=0|1]
    Introduced 8.0.21-ndb-8.0.21
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    When this option is set to 1, ndb_restore allows the primary keys in a table definition to differ from that of the same table in the backup. This may be desirable when backing up and restoring between different schema versions with primary key changes on one or more tables, and it appears that performing the restore operation using ndb_restore is simpler or mor efficient than issuing many ALTER TABLE statements after restoring table schemas and data.

    The following changes in primary key definitions are supported by --allow-pk-changes:

    • Extending the primary key: A non-nullable column that exists in the table schema in the backup becomes part of the table's primary key in the database.

      Important

      When extending a table's primary key, any columns which become part of primary key must not be updated while the backup is being taken; any such updates discovered by ndb_restore cause the restore operation to fail, even when no change in value takes place. In some cases, it may be possible to override this behavior using the --ignore-extended-pk-updates option; see the description of this option for more information.

    • Contracting the primary key (1): A column that is already part of the table's primary key in the backup schema is no longer part of the primary key, but remains in the table.

    • Contracting the primary key (2): A column that is already part of the table's primary key in the backup schema is removed from the table entirely.

    These differences can be combined with other schema differences supported by ndb_restore, including changes to blob and text columns requiring the use of staging tables.

    Basic steps in a typical scenario using primary key schema changes are listed here:

    1. Restore table schemas using ndb_restore --restore-meta

    2. Alter schema to that desired, or create it

    3. Back up the desired schema

    4. Run ndb_restore --disable-indexes using the backup from the previous step, to drop indexes and constraints

    5. Run ndb_restore --allow-pk-changes (possibly along with --ignore-extended-pk-updates, --disable-indexes, and possibly other options as needed) to restore all data

    6. Run ndb_restore --rebuild-indexes using the backup made with the desired schema, to rebuild indexes and constraints

    When extending the primary key, it may be necessary for ndb_restore to use a temporary secondary unique index during the restore operation to map from the old primary key to the new one. Such an index is created only when necessary to apply events from the backup log to a table which has an extended primary key. This index is named NDB$RESTORE_PK_MAPPING, and is created on each table requiring it; it can be shared, if necessary, by multiple instances of ndb_restore instances running in parallel. (Running ndb_restore --rebuild-indexes at the end of the restore process causes this index to be dropped.)

  • --append

    Command-Line Format --append

    When used with the --tab and --print-data options, this causes the data to be appended to any existing files having the same names.

  • --backup-path=dir_name

    Command-Line Format --backup-path=dir_name
    Type Directory name
    Default Value ./

    The path to the backup directory is required; this is supplied to ndb_restore using the --backup-path option, and must include the subdirectory corresponding to the ID backup of the backup to be restored. For example, if the data node's DataDir is /var/lib/mysql-cluster, then the backup directory is /var/lib/mysql-cluster/BACKUP, and the backup files for the backup with the ID 3 can be found in /var/lib/mysql-cluster/BACKUP/BACKUP-3. The path may be absolute or relative to the directory in which the ndb_restore executable is located, and may be optionally prefixed with backup-path=.

    It is possible to restore a backup to a database with a different configuration than it was created from. For example, suppose that a backup with backup ID 12, created in a cluster with two storage nodes having the node IDs 2 and 3, is to be restored to a cluster with four nodes. Then ndb_restore must be run twice—once for each storage node in the cluster where the backup was taken. However, ndb_restore cannot always restore backups made from a cluster running one version of MySQL to a cluster running a different MySQL version.

    Important

    It is not possible to restore a backup made from a newer version of NDB Cluster using an older version of ndb_restore. You can restore a backup made from a newer version of MySQL to an older cluster, but you must use a copy of ndb_restore from the newer NDB Cluster version to do so.

    For example, to restore a cluster backup taken from a cluster running NDB Cluster 7.5.21 to a cluster running NDB Cluster 7.4.31, you must use the ndb_restore that comes with the NDB Cluster 7.5.21 distribution.

    For more rapid restoration, the data may be restored in parallel, provided that there is a sufficient number of cluster connections available. That is, when restoring to multiple nodes in parallel, you must have an [api] or [mysqld] section in the cluster config.ini file available for each concurrent ndb_restore process. However, the data files must always be applied before the logs.

  • --backup-password=password

    Command-Line Format --backup-password=string
    Introduced 8.0.22-ndb-8.0.22
    Type String
    Default Value [none]

    This option specifies a password to be used when decrypting an encrypted backup with the --decrypt option. This must be the same password that was used to encrypt the backup.

    The password can be up to 256 characters in length, and must be enclosed by single or double quotation marks. It can contain any of the ASCII characters having character codes 32, 35, 38, 40-91, 93, 95, and 97-126; in other words, it can use any printable ASCII characters except for !, ', ", $, %, \, and ^.

  • --backupid=#, -b

    Command-Line Format --backupid=#
    Type Numeric
    Default Value none

    This option is used to specify the ID or sequence number of the backup, and is the same number shown by the management client in the Backup backup_id completed message displayed upon completion of a backup. (See Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”.)

    Important

    When restoring cluster backups, you must be sure to restore all data nodes from backups having the same backup ID. Using files from different backups results at best in restoring the cluster to an inconsistent state, and is likely to fail altogether.

    In NDB 8.0.15 and later, this option is required.

  • --connect, -c

    Command-Line Format --connect
    Type String
    Default Value localhost:1186

    Alias for --ndb-connectstring.

  • --decrypt

    Command-Line Format --decrypt
    Introduced 8.0.22-ndb-8.0.22

    Decrypt an encrypted backup using the password supplied by the --backup-password option.

  • --disable-indexes

    Command-Line Format --disable-indexes

    Disable restoration of indexes during restoration of the data from a native NDB backup. Afterwards, you can restore indexes for all tables at once with multithreaded building of indexes using --rebuild-indexes, which should be faster than rebuilding indexes concurrently for very large tables.

  • --dont-ignore-systab-0, -f

    Command-Line Format --dont-ignore-systab-0

    Normally, when restoring table data and metadata, ndb_restore ignores the copy of the NDB system table that is present in the backup. --dont-ignore-systab-0 causes the system table to be restored. This option is intended for experimental and development use only, and is not recommended in a production environment.

  • --exclude-databases=db-list

    Command-Line Format --exclude-databases=db-list
    Type String
    Default Value

    Comma-delimited list of one or more databases which should not be restored.

    This option is often used in combination with --exclude-tables; see that option's description for further information and examples.

  • --exclude-intermediate-sql-tables[=TRUE|FALSE]

    Command-Line Format --exclude-intermediate-sql-tables[=TRUE|FALSE]
    Type Boolean
    Default Value TRUE

    When performing copying ALTER TABLE operations, mysqld creates intermediate tables (whose names are prefixed with #sql-). When TRUE, the --exclude-intermediate-sql-tables option keeps ndb_restore from restoring such tables that may have been left over from these operations. This option is TRUE by default.

  • --exclude-missing-columns

    Command-Line Format --exclude-missing-columns

    It is possible to restore only selected table columns using this option, which causes ndb_restore to ignore any columns missing from tables being restored as compared to the versions of those tables found in the backup. This option applies to all tables being restored. If you wish to apply this option only to selected tables or databases, you can use it in combination with one or more of the --include-* or --exclude-* options described elsewhere in this section to do so, then restore data to the remaining tables using a complementary set of these options.

  • --exclude-missing-tables

    Command-Line Format --exclude-missing-tables

    It is possible to restore only selected tables using this option, which causes ndb_restore to ignore any tables from the backup that are not found in the target database.

  • --exclude-tables=table-list

    Command-Line Format --exclude-tables=table-list
    Type String
    Default Value

    List of one or more tables to exclude; each table reference must include the database name. Often used together with --exclude-databases.

    When --exclude-databases or --exclude-tables is used, only those databases or tables named by the option are excluded; all other databases and tables are restored by ndb_restore.

    This table shows several invocations of ndb_restore usng --exclude-* options (other options possibly required have been omitted for clarity), and the effects these options have on restoring from an NDB Cluster backup:

    Table 23.41 Several invocations of ndb_restore using --exclude-* options, and the effects these options have on restoring from an NDB Cluster backup.

    Option Result
    --exclude-databases=db1 All tables in all databases except db1 are restored; no tables in db1 are restored
    --exclude-databases=db1,db2 (or --exclude-databases=db1 --exclude-databases=db2) All tables in all databases except db1 and db2 are restored; no tables in db1 or db2 are restored
    --exclude-tables=db1.t1 All tables except t1 in database db1 are restored; all other tables in db1 are restored; all tables in all other databases are restored
    --exclude-tables=db1.t2,db2.t1 (or --exclude-tables=db1.t2 --exclude-tables=db2.t1) All tables in database db1 except for t2 and all tables in database db2 except for table t1 are restored; no other tables in db1 or db2 are restored; all tables in all other databases are restored

    You can use these two options together. For example, the following causes all tables in all databases except for databases db1 and db2, and tables t1 and t2 in database db3, to be restored:

    shell> ndb_restore [...] --exclude-databases=db1,db2 --exclude-tables=db3.t1,db3.t2
    

    (Again, we have omitted other possibly necessary options in the interest of clarity and brevity from the example just shown.)

    You can use --include-* and --exclude-* options together, subject to the following rules:

    • The actions of all --include-* and --exclude-* options are cumulative.

    • All --include-* and --exclude-* options are evaluated in the order passed to ndb_restore, from right to left.

    • In the event of conflicting options, the first (rightmost) option takes precedence. In other words, the first option (going from right to left) that matches against a given database or table wins.

    For example, the following set of options causes ndb_restore to restore all tables from database db1 except db1.t1, while restoring no other tables from any other databases:

    --include-databases=db1 --exclude-tables=db1.t1
    

    However, reversing the order of the options just given simply causes all tables from database db1 to be restored (including db1.t1, but no tables from any other database), because the --include-databases option, being farthest to the right, is the first match against database db1 and thus takes precedence over any other option that matches db1 or any tables in db1:

    --exclude-tables=db1.t1 --include-databases=db1
    
  • --fields-enclosed-by=char

    Command-Line Format --fields-enclosed-by=char
    Type String
    Default Value

    Each column value is enclosed by the string passed to this option (regardless of data type; see the description of --fields-optionally-enclosed-by).

  • --fields-optionally-enclosed-by

    Command-Line Format --fields-optionally-enclosed-by
    Type String
    Default Value

    The string passed to this option is used to enclose column values containing character data (such as CHAR, VARCHAR, BINARY, TEXT, or ENUM).

  • --fields-terminated-by=char

    Command-Line Format --fields-terminated-by=char
    Type String
    Default Value \t (tab)

    The string passed to this option is used to separate column values. The default value is a tab character (\t).

  • --hex

    Command-Line Format --hex

    If this option is used, all binary values are output in hexadecimal format.

  • --ignore-extended-pk-updates

    Command-Line Format --ignore-extended-pk-updates[=0|1]
    Introduced 8.0.21-ndb-8.0.21
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1

    When using --allow-pk-changes, columns which become part of a table's primary key must not be updated while the backup is being taken; such columns should keep the same values from the time values are inserted into them until the rows containing the values are deleted. If ndb_restore encounters updates to these columns when restoring a backup, the restore fails. Because some applications may set values for all columns when updating a row, even when some column values are not changed, the backup may include log events appearing to update columns which are not in fact modified. In such cases you can set --ignore-extended-pk-updates to 1, forcing ndb_restore to ignore such updates.

    Important

    When causing these updates to be ignored, the user is responsible for ensuring that there are no updates to the values of any columns that become part of the primary key.

    For more information, see the description of --allow-pk-changes.

  • --include-databases=db-list

    Command-Line Format --include-databases=db-list
    Type String
    Default Value

    Comma-delimited list of one or more databases to restore. Often used together with --include-tables; see the description of that option for further information and examples.

  • --include-stored-grants

    Command-Line Format --include-stored-grants
    Introduced 8.0.19-ndb-8.0.19
    Type Boolean
    Default Value FALSE

    In NDB 8.0.19 and later, ndb_restore does not by default restore shared users and grants (see Section 23.5.12, “Distributed MySQL Privileges with NDB_STORED_USER”) to the ndb_sql_metadata table. Specifying this option causes it to do so.

  • --include-tables=table-list

    Command-Line Format --include-tables=table-list
    Type String
    Default Value

    Comma-delimited list of tables to restore; each table reference must include the database name.

    When --include-databases or --include-tables is used, only those databases or tables named by the option are restored; all other databases and tables are excluded by ndb_restore, and are not restored.

    The following table shows several invocations of ndb_restore using --include-* options (other options possibly required have been omitted for clarity), and the effects these have on restoring from an NDB Cluster backup:

    Table 23.42 Several invocations of ndb_restore using --include-* options, and their effects on restoring from an NDB Cluster backup.

    Option Result
    --include-databases=db1 Only tables in database db1 are restored; all tables in all other databases are ignored
    --include-databases=db1,db2 (or --include-databases=db1 --include-databases=db2) Only tables in databases db1 and db2 are restored; all tables in all other databases are ignored
    --include-tables=db1.t1 Only table t1 in database db1 is restored; no other tables in db1 or in any other database are restored
    --include-tables=db1.t2,db2.t1 (or --include-tables=db1.t2 --include-tables=db2.t1) Only the table t2 in database db1 and the table t1 in database db2 are restored; no other tables in db1, db2, or any other database are restored

    You can also use these two options together. For example, the following causes all tables in databases db1 and db2, together with the tables t1 and t2 in database db3, to be restored (and no other databases or tables):

    shell> ndb_restore [...] --include-databases=db1,db2 --include-tables=db3.t1,db3.t2
    

    (Again we have omitted other, possibly required, options in the example just shown.)

    It also possible to restore only selected databases, or selected tables from a single database, without any --include-* (or --exclude-*) options, using the syntax shown here:

    ndb_restore other_options db_name,[db_name[,...] | tbl_name[,tbl_name][,...]]
    

    In other words, you can specify either of the following to be restored:

    • All tables from one or more databases

    • One or more tables from a single database

  • --lines-terminated-by=char

    Command-Line Format --lines-terminated-by=char
    Type String
    Default Value \n (linebreak)

    Specifies the string used to end each line of output. The default is a linefeed character (\n).

  • --lossy-conversions, -L

    Command-Line Format --lossy-conversions
    Type Boolean
    Default Value FALSE (If option is not used)

    This option is intended to complement the --promote-attributes option. Using --lossy-conversions allows lossy conversions of column values (type demotions or changes in sign) when restoring data from backup. With some exceptions, the rules governing demotion are the same as for MySQL replication; see Section 17.5.1.9.2, “Replication of Columns Having Different Data Types”, for information about specific type conversions currently supported by attribute demotion.

    ndb_restore reports any truncation of data that it performs during lossy conversions once per attribute and column.

  • --no-binlog

    Command-Line Format --no-binlog

    This option prevents any connected SQL nodes from writing data restored by ndb_restore to their binary logs.

  • --no-restore-disk-objects, -d

    Command-Line Format --no-restore-disk-objects
    Type Boolean
    Default Value FALSE

    This option stops ndb_restore from restoring any NDB Cluster Disk Data objects, such as tablespaces and log file groups; see Section 23.5.10, “NDB Cluster Disk Data Tables”, for more information about these.

  • --no-upgrade, -u

    Command-Line Format --no-upgrade

    When using ndb_restore to restore a backup, VARCHAR columns created using the old fixed format are resized and recreated using the variable-width format now employed. This behavior can be overridden by specifying --no-upgrade.

  • --ndb-nodegroup-map=map, -z

    Command-Line Format --ndb-nodegroup-map=map

    This option can be used to restore a backup taken from one node group to a different node group. Its argument is a list of the form source_node_group, target_node_group.

  • --nodeid=#, -n

    Command-Line Format --nodeid=#
    Type Numeric
    Default Value none

    Specify the node ID of the data node on which the backup was taken.

    When restoring to a cluster with different number of data nodes from that where the backup was taken, this information helps identify the correct set or sets of files to be restored to a given node. (In such cases, multiple files usually need to be restored to a single data node.) See Section 23.4.23.2, “Restoring to a different number of data nodes”, for additional information and examples.

    In NDB 8.0.15 and later, this option is required.

  • --num-slices=#

    Command-Line Format --num-slices=#
    Introduced 8.0.20-ndb-8.0.20
    Type Integer
    Default Value 1
    Minimum Value 1
    Maximum Value 1024

    When restoring a backup by slices, this option sets the number of slices into which to divide the backup. This allows multiple instances of ndb_restore to restore disjoint subsets in parallel, potentially reducing the amount of time required to perform the restore operation.

    A slice is a subset of the data in a given backup; that is, it is a set of fragments having the same slice ID, specified using the --slice-id option. The two options must always be used together, and the value set by --slice-id must always be less than the number of slices.

    ndb_restore encounters fragments and assigns each one a fragment counter. When restoring by slices, a slice ID is assigned to each fragment; this slice ID is in the range 0 to 1 less than the number of slices. For a table that is not a BLOB table, the slice to which a given fragment belongs is determined using the formula shown here:

    [slice_ID] = [fragment_counter] % [number_of_slices]
    

    For a BLOB table, a fragment counter is not used; the fragment number is used instead, along with the ID of the main table for the BLOB table (recall that NDB stores BLOB values in a separate table internally). In this case, the slice ID for a given fragment is calculated as shown here:

    [slice_ID] =
    ([main_table_ID] + [fragment_ID]) % [number_of_slices]
    

    Thus, restoring by N slices means running N instances of ndb_restore, all with --num-slices=N (along with any other necessary options) and one each with --slice-id=1, --slice-id=2, --slice-id=3, and so on through slice-id=N-1.

    Example.  Assume that you want to restore a backup named BACKUP-1, found in the default directory /var/lib/mysql-cluster/BACKUP/BACKUP-3 on the node file system on each data node, to a cluster with four data nodes having the node IDs 1, 2, 3, and 4. To perform this operation using five slices, execute the sets of commands shown in the following list:

    1. Restore the cluster metadata using ndb_restore as shown here:

      shell> ndb_restore -b 1 -n 1 -m --disable-indexes --backup-path=/home/ndbuser/backups
      
    2. Restore the cluster data to the data nodes invoking ndb_restore as shown here:

      shell> ndb_restore -b 1 -n 1 -r --num-slices=5 --slice-id=0 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 1 -r --num-slices=5 --slice-id=1 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 1 -r --num-slices=5 --slice-id=2 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 1 -r --num-slices=5 --slice-id=3 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 1 -r --num-slices=5 --slice-id=4 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      
      shell> ndb_restore -b 1 -n 2 -r --num-slices=5 --slice-id=0 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 2 -r --num-slices=5 --slice-id=1 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 2 -r --num-slices=5 --slice-id=2 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 2 -r --num-slices=5 --slice-id=3 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 2 -r --num-slices=5 --slice-id=4 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      
      shell> ndb_restore -b 1 -n 3 -r --num-slices=5 --slice-id=0 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 3 -r --num-slices=5 --slice-id=1 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 3 -r --num-slices=5 --slice-id=2 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 3 -r --num-slices=5 --slice-id=3 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 3 -r --num-slices=5 --slice-id=4 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      
      shell> ndb_restore -b 1 -n 4 -r --num-slices=5 --slice-id=0 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 4 -r --num-slices=5 --slice-id=1 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 4 -r --num-slices=5 --slice-id=2 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 4 -r --num-slices=5 --slice-id=3 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      shell> ndb_restore -b 1 -n 4 -r --num-slices=5 --slice-id=4 --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      

      All of the commands just shown in this step can be executed in parallel, provided there are enough slots for connections to the cluster (see the description for the --backup-path option).

    3. Restore indexes as usual, as shown here:

      shell> ndb_restore -b 1 -n 1 --rebuild-indexes --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      
    4. Finally, restore the epoch, using the command shown here:

      shell> ndb_restore -b 1 -n 1 --restore-epoch --backup-path=/var/lib/mysql-cluster/BACKUP/BACKUP-1
      

    You should use slicing to restore the cluster data only; it is not necessary to employ --num-slices or --slice-id when restoring the metadata, indexes, or epoch information. If either or both of these options are used with the ndb_restore options controlling restoration of these, the program ignores them.

    The effects of using the --parallelism option on the speed of restoration are independent of those produced by slicing or parallel restoration using multiple instances of ndb_restore (--parallelism specifies the number of parallel transactions executed by a single ndb_restore thread), but it can be used together with either or both of these. You should be aware that increasing --parallelism causes ndb_restore to impose a greater load on the cluster; if the system can handle this, restoration should complete even more quickly.

    The value of --num-slices is not directly dependent on values relating to hardware such as number of CPUs or CPU cores, amount of RAM, and so forth, nor does it depend on the number of LDMs.

    It is possible to employ different values for this option on different data nodes as part of the same restoration; doing so should not in and of itself produce any ill effects.

  • --parallelism=#, -p

    Command-Line Format --parallelism=#
    Type Numeric
    Default Value 128
    Minimum Value 1
    Maximum Value 1024

    ndb_restore uses single-row transactions to apply many rows concurrently. This parameter determines the number of parallel transactions (concurrent rows) that an instance of ndb_restore tries to use. By default, this is 128; the minimum is 1, and the maximum is 1024.

    The work of performing the inserts is parallelized across the threads in the data nodes involved. This mechanism is employed for restoring bulk data from the .Data file—that is, the fuzzy snapshot of the data; it is not used for building or rebuilding indexes. The change log is applied serially; index drops and builds are DDL operations and handled separately. There is no thread-level parallelism on the client side of the restore.

  • --preserve-trailing-spaces, -P

    Command-Line Format --preserve-trailing-spaces

    Cause trailing spaces to be preserved when promoting a fixed-width character data type to its variable-width equivalent—that is, when promoting a CHAR column value to VARCHAR, or a BINARY column value to VARBINARY. Otherwise, any trailing spaces are dropped from such column values when they are inserted into the new columns.

    Note

    Although you can promote CHAR columns to VARCHAR and BINARY columns to VARBINARY, you cannot promote VARCHAR columns to CHAR or VARBINARY columns to BINARY.

  • --print

    Command-Line Format --print
    Type Boolean
    Default Value FALSE

    Causes ndb_restore to print all data, metadata, and logs to stdout. Equivalent to using the --print-data, --print-meta, and --print-log options together.

    Note

    Use of --print or any of the --print_* options is in effect performing a dry run. Including one or more of these options causes any output to be redirected to stdout; in such cases, ndb_restore makes no attempt to restore data or metadata to an NDB Cluster.

  • --print-data

    Command-Line Format --print-data
    Type Boolean
    Default Value FALSE

    Cause ndb_restore to direct its output to stdout. Often used together with one or more of --tab, --fields-enclosed-by, --fields-optionally-enclosed-by, --fields-terminated-by, --hex, and --append.

    TEXT and BLOB column values are always truncated. Such values are truncated to the first 256 bytes in the output. This cannot currently be overridden when using --print-data.

  • --print-log

    Command-Line Format --print-log
    Type Boolean
    Default Value FALSE

    Cause ndb_restore to output its log to stdout.

  • --print-meta

    Command-Line Format --print-meta
    Type Boolean
    Default Value FALSE

    Print all metadata to stdout.

  • print-sql-log

    Command-Line Format --print-sql-log
    Type Boolean
    Default Value FALSE

    Log SQL statements to stdout. Use the option to enable; normally this behavior is disabled. The option checks before attempting to log whether all the tables being restored have explicitly defined primary keys; queries on a table having only the hidden primary key implemented by NDB cannot be converted to valid SQL.

    This option does not work with tables having BLOB columns.

  • --progress-frequency=N

    Command-Line Format --progress-frequency=#
    Type Numeric
    Default Value 0
    Minimum Value 0
    Maximum Value 65535

    Print a status report each N seconds while the backup is in progress. 0 (the default) causes no status reports to be printed. The maximum is 65535.

  • --promote-attributes, -A

    Command-Line Format --promote-attributes

    ndb_restore supports limited attribute promotion in much the same way that it is supported by MySQL replication; that is, data backed up from a column of a given type can generally be restored to a column using a larger, similar type. For example, data from a CHAR(20) column can be restored to a column declared as VARCHAR(20), VARCHAR(30), or CHAR(30); data from a MEDIUMINT column can be restored to a column of type INT or BIGINT. See Section 17.5.1.9.2, “Replication of Columns Having Different Data Types”, for a table of type conversions currently supported by attribute promotion.

    Attribute promotion by ndb_restore must be enabled explicitly, as follows:

    1. Prepare the table to which the backup is to be restored. ndb_restore cannot be used to re-create the table with a different definition from the original; this means that you must either create the table manually, or alter the columns which you wish to promote using ALTER TABLE after restoring the table metadata but before restoring the data.

    2. Invoke ndb_restore with the --promote-attributes option (short form -A) when restoring the table data. Attribute promotion does not occur if this option is not used; instead, the restore operation fails with an error.

    When converting between character data types and TEXT or BLOB, only conversions between character types (CHAR and VARCHAR) and binary types (BINARY and VARBINARY) can be performed at the same time. For example, you cannot promote an INT column to BIGINT while promoting a VARCHAR column to TEXT in the same invocation of ndb_restore.

    Converting between TEXT columns using different character sets is not supported, and is expressly disallowed.

    When performing conversions of character or binary types to TEXT or BLOB with ndb_restore, you may notice that it creates and uses one or more staging tables named table_name$STnode_id. These tables are not needed afterwards, and are normally deleted by ndb_restore following a successful restoration.

  • --rebuild-indexes

    Command-Line Format --rebuild-indexes

    Enable multithreaded rebuilding of the ordered indexes while restoring a native NDB backup. The number of threads used for building ordered indexes by ndb_restore with this option is controlled by the BuildIndexThreads data node configuration parameter and the number of LDMs.

    It is necessary to use this option only for the first run of ndb_restore; this causes all ordered indexes to be rebuilt without using --rebuild-indexes again when restoring subsequent nodes. You should use this option prior to inserting new rows into the database; otherwise, it is possible for a row to be inserted that later causes a unique constraint violation when trying to rebuild the indexes.

    Building of ordered indices is parallelized with the number of LDMs by default. Offline index builds performed during node and system restarts can be made faster using the BuildIndexThreads data node configuration parameter; this parameter has no effect on dropping and rebuilding of indexes by ndb_restore, which is performed online.

    Rebuilding of unique indexes uses disk write bandwidth for redo logging and local checkpointing. An insufficient amount of this bandwith can lead to redo buffer overload or log overload errors. In such cases you can run ndb_restore --rebuild-indexes again; the process resumes at the point where the error occurred. You can also do this when you have encountered temporary errors. You can repeat execution of ndb_restore --rebuild-indexes indefinitely; you may be able to stop such errors by reducing the value of --parallelism. If the problem is insufficient space, you can increase the size of the redo log (FragmentLogFileSize node configuration parameter), or you can increase the speed at which LCPs are performed (MaxDiskWriteSpeed and related parameters), in order to free space more quickly.

  • --remap-column=db.tbl.col:fn:args

    Command-Line Format --remap-column=[db].[tbl].[col]:[fn]:[args]
    Introduced 8.0.21-ndb-8.0.21
    Type String
    Default Value [none]

    When used together with --restore-data, this option applies a function to the value of the indicated column. Values in the argument string are listed here:

    • db: Database name, following any renames performed by --rewrite-database.

    • tbl: Table name.

    • col: Name of the column to be updated. This column must be of type INT or BIGINT. The column can also be but is not required to be UNSIGNED.

    • fn: Function name; currently, the only supported name is offset.

    • args: Arguments supplied to the function. Currently, only a single argument, the size of the offset to be added by the offset function, is supported. Negative values are supported. The size of the argument cannot exceed that of the signed variant of the column's type; for example, if col is an INT column, then the allowed range of the argument passed to the offset function is -2147483648 to 2147483647 (see Section 11.1.2, “Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT”).

      If applying the offset value to the column would cause an overflow or underflow, the restore operation fails. This could happen, for example, if the column is a BIGINT, and the option attempts to apply an offset value of 8 on a row in which the column value is 4294967291, since 4294967291 + 8 = 4294967299 > 4294967295.

    This option can be useful when you wish to merge data stored in multiple source instances of NDB Cluster (all using the same schema) into a single destination NDB Cluster, using NDB native backup (see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”) and ndb_restore to merge the data, where primary and unique key values are overlapping between source clusters, and it is necessary as part of the process to remap these values to ranges that do not overlap. It may also be necessary to preserve other relationships between tables. To fulfill such requirements, it is possible to use the option multiple times in the same invocation of ndb_restore to remap columns of different tables, as shown here:

    shell> ndb_restore --restore-data --remap-column=hr.employee.id:offset:1000 \
        --remap-column=hr.manager.id:offset:1000 --remap-column=hr.firstaiders.id:offset:1000
    

    (Other options not shown here may also be used.)

    --remap-column can also be used to update multiple columns of the same table. Combinations of multiple tables and columns are possible. Different offset values can also be used for different columns of the same table, like this:

    shell> ndb_restore --restore-data --remap-column=hr.employee.salary:offset:10000 \
        --remap-column=hr.employee.hours:offset:-10
    

    When source backups contain duplicate tables which should not be merged, you can handle this by using --exclude-tables, --exclude-databases, or by some other means in your application.

    Information about the structure and other characteristics of tables to be merged can obtained using SHOW CREATE TABLE; the ndb_desc tool; and MAX(), MIN(), LAST_INSERT_ID(), and other MySQL functions.

    Replication of changes from merged to unmerged tables, or from unmerged to merged tables, in separate instances of NDB Cluster is not supported.

  • --restore-data, -r

    Command-Line Format --restore-data
    Type Boolean
    Default Value FALSE

    Output NDB table data and logs.

  • --restore-epoch, -e

    Command-Line Format --restore-epoch

    Add (or restore) epoch information to the cluster replication status table. This is useful for starting replication on an NDB Cluster replica. When this option is used, the row in the mysql.ndb_apply_status having 0 in the id column is updated if it already exists; such a row is inserted if it does not already exist. (See Section 23.6.9, “NDB Cluster Backups With NDB Cluster Replication”.)

  • --restore-meta, -m

    Command-Line Format --restore-meta
    Type Boolean
    Default Value FALSE

    This option causes ndb_restore to print NDB table metadata.

    The first time you run the ndb_restore restoration program, you also need to restore the metadata. In other words, you must re-create the database tables—this can be done by running it with the --restore-meta (-m) option. Restoring the metadata need be done only on a single data node; this is sufficient to restore it to the entire cluster.

    In older versions of NDB Cluster, tables whose schemas were restored using this option used the same number of partitions as they did on the original cluster, even if it had a differing number of data nodes from the new cluster. In NDB 8.0, when restoring metadata, this is no longer an issue; ndb_restore now uses the default number of partitions for the target cluster, unless the number of local data manager threads is also changed from what it was for data nodes in the original cluster.

    When using this option in NDB 8.0.16 or later, it is recommended that auto synchronization be disabled by setting ndb_metadata_check=OFF until ndb_restore has completed restoring the metadata, after which it can it turned on again to synchronize objects newly created in the NDB dictionary.

    Note

    The cluster should have an empty database when starting to restore a backup. (In other words, you should start the data nodes with --initial prior to performing the restore.)

  • --restore-privilege-tables

    Command-Line Format --restore-privilege-tables
    Deprecated 8.0.16-ndb-8.0.16
    Type Boolean
    Default Value FALSE (If option is not used)

    ndb_restore does not by default restore distributed MySQL privilege tables created in releases of NDB Cluster prior to version 8.0, which does not support distrubuted privileges as implemented in NDB 7.6 and earlier. This option causes ndb_restore to restore them.

    In NDB 8.0.16 and later, such tables are not used for access control; as part of the MySQL server's upgrade process, the server creates InnoDB copies of these tables local to itself. For more information, see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”, as well as Section 6.2.3, “Grant Tables”.

  • --rewrite-database=olddb,newdb

    Command-Line Format --rewrite-database=olddb,newdb
    Type String
    Default Value none

    This option makes it possible to restore to a database having a different name from that used in the backup. For example, if a backup is made of a database named products, you can restore the data it contains to a database named inventory, use this option as shown here (omitting any other options that might be required):

    shell> ndb_restore --rewrite-database=product,inventory
    

    The option can be employed multiple times in a single invocation of ndb_restore. Thus it is possible to restore simultaneously from a database named db1 to a database named db2 and from a database named db3 to one named db4 using --rewrite-database=db1,db2 --rewrite-database=db3,db4. Other ndb_restore options may be used between multiple occurrences of --rewrite-database.

    In the event of conflicts between multiple --rewrite-database options, the last --rewrite-database option used, reading from left to right, is the one that takes effect. For example, if --rewrite-database=db1,db2 --rewrite-database=db1,db3 is used, only --rewrite-database=db1,db3 is honored, and --rewrite-database=db1,db2 is ignored. It is also possible to restore from multiple databases to a single database, so that --rewrite-database=db1,db3 --rewrite-database=db2,db3 restores all tables and data from databases db1 and db2 into database db3.

    Important

    When restoring from multiple backup databases into a single target database using --rewrite-database, no check is made for collisions between table or other object names, and the order in which rows are restored is not guaranteed. This means that it is possible in such cases for rows to be overwritten and updates to be lost.

  • --skip-broken-objects

    Command-Line Format --skip-broken-objects

    This option causes ndb_restore to ignore corrupt tables while reading a native NDB backup, and to continue restoring any remaining tables (that are not also corrupted). Currently, the --skip-broken-objects option works only in the case of missing blob parts tables.

  • --skip-table-check, -s

    Command-Line Format --skip-table-check

    It is possible to restore data without restoring table metadata. By default when doing this, ndb_restore fails with an error if a mismatch is found between the table data and the table schema; this option overrides that behavior.

    Some of the restrictions on mismatches in column definitions when restoring data using ndb_restore are relaxed; when one of these types of mismatches is encountered, ndb_restore does not stop with an error as it did previously, but rather accepts the data and inserts it into the target table while issuing a warning to the user that this is being done. This behavior occurs whether or not either of the options --skip-table-check or --promote-attributes is in use. These differences in column definitions are of the following types:

    • Different COLUMN_FORMAT settings (FIXED, DYNAMIC, DEFAULT)

    • Different STORAGE settings (MEMORY, DISK)

    • Different default values

    • Different distribution key settings

  • --skip-unknown-objects

    Command-Line Format --skip-unknown-objects

    This option causes ndb_restore to ignore any schema objects it does not recognize while reading a native NDB backup. This can be used for restoring a backup made from a cluster running (for example) NDB 7.6 to a cluster running NDB Cluster 7.5.

  • --slice-id=#

    Command-Line Format --slice-id=#
    Introduced 8.0.20-ndb-8.0.20
    Type Integer
    Default Value 0
    Minimum Value 0
    Maximum Value 1023

    When restoring by slices, this is the ID of the slice to restore. This option is always used together with --num-slices, and its value must be always less than that of --num-slices.

    For more information, see the description of the --num-slices elsewhere in this section.

  • --tab=dir_name, -T dir_name

    Command-Line Format --tab=dir_name
    Type Directory name

    Causes --print-data to create dump files, one per table, each named tbl_name.txt. It requires as its argument the path to the directory where the files should be saved; use . for the current directory.

  • --verbose=#

    Command-Line Format --verbose=#
    Type Numeric
    Default Value 1
    Minimum Value 0
    Maximum Value 255

    Sets the level for the verbosity of the output. The minimum is 0; the maximum is 255. The default value is 1.

Error reporting.  ndb_restore reports both temporary and permanent errors. In the case of temporary errors, it may able to recover from them, and reports Restore successful, but encountered temporary error, please look at configuration in such cases.

Important

After using ndb_restore to initialize an NDB Cluster for use in circular replication, binary logs on the SQL node acting as the replica are not automatically created, and you must cause them to be created manually. To cause the binary logs to be created, issue a SHOW TABLES statement on that SQL node before running START SLAVE. This is a known issue in NDB Cluster.

23.4.23.1 Restoring an NDB Backup to a Different Version of NDB Cluster

The following two sections provide information about restoring a native NDB backup to a different version of NDB Cluster from the version in which the backup was taken.

In addition, you should consult Section 23.2.7, “Upgrading and Downgrading NDB Cluster”, for other issues you may encounter when attempting to restore an NDB backup to a cluster running a different version of the NDB software.

It is also advisable to review What is New in NDB Cluster 8.0, as well as Section 2.11.4, “Changes in MySQL 8.0”, for other changes between NDB 8.0 and previous versions of NDB Cluster that may be relevant to your particular circumstances.

23.4.23.1.1 Restoring an NDB backup to a previous version of NDB Cluster

You may encounter issues when restoring a backup taken from a later version of NDB Cluster to a previous one, due to the use of features which do not exist in the earlier version. Some of these issues are listed here:

  • Tables created in NDB 8.0 by default use the utf8mb4_ai_ci character set, which is not available in NDB 7.6 and earlier, and so cannot be read by an ndb_restore binary from one of these earlier versions. In such cases, it is necessary to alter any tables using utf8mb4_ai_ci so that they use a character set supported in the older version prior to performing the backup.

  • Due to changes in how the MySQL Server and NDB handle table metadata, tables created or altered using the included MySQL server binary from NDB 8.0.14 or later cannot be restored using ndb_restore to an earlier version of NDB Cluster. Such tables use .sdi files which are not understood by older versions of mysqld.

    A backup taken in NDB 8.0.14 or later of tables which were created in NDB 8.0.13 or earlier, and which have not been altered since upgrading to NDB 8.0.14 or later, should be restorable to older versions of NDB Cluster.

    Since it is possible to restore metadata and table data separately, you can in such cases restore the table schemas from a dump made using mysqldump, or by executing the necessary CREATE TABLE statements manually, then import only the table data using ndb_restore with the --restore-data option.

  • Encrypted backups created in NDB 8.0.22 and later cannot be restored using ndb_restore from NDB 8.0.21 or earlier.

  • The NDB_STORED_USER privilege is not supported prior to NDB 8.0.18.

  • NDB Cluster 8.0.18 and later supports up to 144 data nodes, while earlier versions support a maximum of only 48 data nodes. See Section 23.4.23.2.1, “Restoring to Fewer Nodes Than the Original”, for information with situations in which this incompatibility causes an issue.

23.4.23.1.2 Restoring an NDB backup to a later version of NDB Cluster

In general, it should be possible to restore a backup created using the ndb_mgm client START BACKUP command in an older version of NDB to a newer version, provided that you use the ndb_restore binary that comes with the newer version. (It may be possible to use the older version of ndb_restore, but this is not recommended.) Additional potential issues are listed here:

  • When restoring the metadata from a backup (--restore-meta option), ndb_restore normally attempts to reproduce the captured table schema exactly as it was when the backup was taken.

    Tables created in versions of NDB prior to 8.0.14 use .frm files for their metadata. These files can be read by the mysqld in NDB 8.0.14 and later, which can use the information contained therein to create the .sdi files used by the MySQL data dictionary in later versions.

  • When restoring an older backup to a newer version of NDB, it may not be possible to take advantage of newer features such as hashmap partitioning, greater number of hashmap buckets, read backup, and different partitioning layouts. For this reason, it may be preferable to restore older schemas using mysqldump and the mysql client, which allows NDB to make use of the new schema features.

  • Tables using the old temporal types which did not support fractional seconds (used prior to MySQL 5.6.4 and NDB 7.3.31) cannot be restored to NDB 8.0 using ndb_restore. You can check such tables using CHECK TABLE, and then upgrade them to the newer temporal column format, if necessary, using REPAIR TABLE in the mysql client; this must be done prior to taking the backup. See Section 2.11.5, “Preparing Your Installation for Upgrade”, for more information.

    You also also restore such tables using a dump created with mysqldump.

  • Distributed grant tables created in NDB 7.6 and earlier are not supported in NDB 8.0. Such tables can be restored to an NDB 8.0 cluster, but they have no effect on access control.

23.4.23.2 Restoring to a different number of data nodes

It is possible to restore from an NDB backup to a cluster having a different number of data nodes than the original from which the backup was taken. The following two sections discuss, respectively, the cases where the target cluster has a lesser or greater number of data nodes than the source of the backup.

23.4.23.2.1 Restoring to Fewer Nodes Than the Original

You can restore to a cluster having fewer data nodes than the original provided that the larger number of nodes is an even multiple of the smaller number. In the following example, we use a backup taken on a cluster having four data nodes to a cluster having two data nodes.

  1. The management server for the original cluster is on host host10. The original cluster has four data nodes, with the node IDs and host names shown in the following extract from the management server's config.ini file:

    [ndbd]
    NodeId=2
    HostName=host2
    
    [ndbd]
    NodeId=4
    HostName=host4
    
    [ndbd]
    NodeId=6
    HostName=host6
    
    [ndbd]
    NodeId=8
    HostName=host8
    

    We assume that each data node was originally started with ndbmtd --ndb-connectstring=host10 or the equivalent.

  2. Perform a backup in the normal manner. See Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup”, for information about how to do this.

  3. The files created by the backup on each data node are listed here, where N is the node ID and B is the backup ID.

    • BACKUP-B-0.N.Data

    • BACKUP-B.N.ctl

    • BACKUP-B.N.log

    These files are found under BackupDataDir/BACKUP/BACKUP-B, on each data node. For the rest of this example, we assume that the backup ID is 1.

    Have all of these files available for later copying to the new data nodes (where they can be accessed on the data node's local file system by ndb_restore). It is simplest to copy them all to a single location; we assume that this is what you have done.

  4. The management server for the target cluster is on host host20, and the target has two data nodes, with the node IDs and host names shown, from the management server config.ini file on host20:

    [ndbd]
    NodeId=3
    hostname=host3
    
    [ndbd]
    NodeId=5
    hostname=host5
    

    Each of the data node processes on host3 and host5 should be started with ndbmtd -c host20 --initial or the equivalent, so that the new (target) cluster starts with clean data node file systems.

  5. Copy two different sets of two backup files to each of the target data nodes. For this example, copy the backup files from nodes 2 and 4 from the original cluster to node 3 in the target cluster. These files are listed here:

    • BACKUP-1-0.2.Data

    • BACKUP-1.2.ctl

    • BACKUP-1.2.log

    • BACKUP-1-0.6.Data

    • BACKUP-1.6.ctl

    • BACKUP-1.6.log

    Then copy the backup files from nodes 6 and 8 to node 5; these files are shown in the following list:

    • BACKUP-1-0.4.Data

    • BACKUP-1.4.ctl

    • BACKUP-1.4.log

    • BACKUP-1-0.8.Data

    • BACKUP-1.8.ctl

    • BACKUP-1.8.log

    For the remainder of this example, we assume that the respective backup files have been saved to the directory /BACKUP-1 on each of nodes 3 and 5.

  6. On each of the two target data nodes, you must restore from both sets of backups. First, restore the backups from nodes 2 and 4 to node 3 by invoking ndb_restore on host3 as shown here:

    shell> ndb_restore -c host20 --nodeid=2 --backupid=1 --restore-data --backup-path=/BACKUP-1
    
    shell> ndb_restore -c host20 --nodeid=4 --backupid=1 --restore-data --backup-path=/BACKUP-1
    

    Then restore the backups from nodes 6 and 8 to node 5 by invoking ndb_restore on host5, like this:

    shell> ndb_restore -c host20 --nodeid=6 --backupid=1 --restore-data --backup-path=/BACKUP-1
    
    shell> ndb_restore -c host20 --nodeid=8 --backupid=1 --restore-data --backup-path=/BACKUP-1
    
23.4.23.2.2 Restoring to More Nodes Than the Original

The node ID specified for a given ndb_restore command is that of the node in the original backup and not that of the data node to restore it to. When performing a backup using the method described in this section, ndb_restore connects to the management server and obtains a list of data nodes in the cluster the backup is being restored to. The restored data is distributed accordingly, so that the number of nodes in the target cluster does not need to be to be known or calculated when performing the backup.

Note

When changing the total number of LCP threads or LQH threads per node group, you should recreate the schema from backup created using mysqldump.

  1. Create the backup of the data. You can do this by invoking the ndb_mgm client START BACKUP command from the system shell, like this:

    shell> ndb_mgm -e "START BACKUP 1"
    

    This assumes that the desired backup ID is 1.

  2. Create a backup of the schema. This step is necessary only if the total number of LCP threads or LQH threads per node group is changed.

    shell> mysqldump --no-data --routines --events --triggers --databases > myschema.sql
    
    Important

    Once you have created the NDB native backup using ndb_mgm, you must not make any schema changes before creating the backup of the schema, if you do so.

  3. Copy the backup directory to the new cluster. For example if the backup you want to restore has ID 1 and BackupDataDir = /backups/node_nodeid, then the path to the backup on this node is /backups/node_1/BACKUP/BACKUP-1. Inside this directory there are three files, listed here:

    • BACKUP-1-0.1.Data

    • BACKUP-1.1.ctl

    • BACKUP-1.1.log

    You should copy the entire directory to the new node.

    If you needed to create a schema file, copy this to a location on an SQL node where it can be read by mysqld.

There is no requirement for the backup to be restored from a specific node or nodes.

To restore from the backup just created, perform the following steps:

  1. Restore the schema.

    • If you created a separate schema backup file using mysqldump, import this file using the mysql client, similar to what is shown here:

      shell> mysql < myschema.sql
      

      When importing the schema file, you may need to specify the --user and --password options (and possibly others) in addition to what is shown, in order for the mysql client to be able to connect to the MySQL server.

    • If you did not need to create a schema file, you can re-create the schema using ndb_restore --restore-meta (short form -m), similar to what is shown here:

      shell> ndb_restore --nodeid=1 --backupid=1 --restore-meta --backup-path=/backups/node_1/BACKUP/BACKUP-1
      

      ndb_restore must be able to contact the management server; add the --ndb-connectstring option if and as needed to make this possible.

  2. Restore the data. This needs to be done once for each data node in the original cluster, each time using that data node's node ID. Assuming that there were 4 data nodes originally, the set of commands required would look something like this:

    ndb_restore --nodeid=1 --backupid=1 --restore-data --backup-path=/backups/node_1/BACKUP/BACKUP-1 --disable-indexes
    ndb_restore --nodeid=2 --backupid=1 --restore-data --backup-path=/backups/node_2/BACKUP/BACKUP-1 --disable-indexes
    ndb_restore --nodeid=3 --backupid=1 --restore-data --backup-path=/backups/node_3/BACKUP/BACKUP-1 --disable-indexes
    ndb_restore --nodeid=4 --backupid=1 --restore-data --backup-path=/backups/node_4/BACKUP/BACKUP-1 --disable-indexes
    

    These can be run in parallel.

    Be sure to add the --ndb-connectstring option as needed.

  3. Rebuild the indexes. These were disabled by the --disable-indexes option used in the commands just shown. Recreating the indexes avoids errors due to the restore not being consistent at all points. Rebuilding the indexes can also improve performance in some cases. To rebuild the indexes, execute the following command once, on a single node:

    shell> ndb_restore --nodeid=1 --backupid=1 --backup-path=/backups/node_1/BACKUP/BACKUP-1 --rebuild-indexes
    

    As mentioned previously, you may need to add the --ndb-connectstring option, so that ndb_restore can contact the management server.

23.4.23.3 Restoring from a backup taken in parallel

Beginning with NDB Cluster 8.0.16, it is possible to take parallel backups on each data node using ndbmtd with multiple LDMs (see Section 23.5.8.5, “Taking an NDB Backup with Parallel Data Nodes”). The next two sections describe how to restore backups that were taken in this fashion.

23.4.23.3.1 Restoring a parallel backup in parallel

Restoring a parallel backup in parallel requires an ndb_restore binary from an NDB Cluster distribution version 8.0.16 or later. The process is not substantially different from that outlined in the general usage section under the description of the ndb_restore program, and consists of executing ndb_restore twice, similarly to what is shown here:

shell> ndb_restore -n 1 -b 1 -m --backup-path=path/to/backup_dir/BACKUP/BACKUP-backup_id
shell> ndb_restore -n 1 -b 1 -r --backup-path=path/to/backup_dir/BACKUP/BACKUP-backup_id

backup_id is the ID of the backup to be restored. In the general case, no additional special arguments are required; ndb_restore always checks for the existence of parallel subdirectories under the directory indicated by the --backup-path option and restores the metadata (serially) and then the table data (in parallel).

23.4.23.3.2 Restoring a parallel backup serially

It is possible to restore a backup that was made using parallelism on the data nodes in serial fashion. To do this, invoke ndb_restore with --backup-path pointing to the subdirectories created by each LDM under the main backup directory, once to any one of the subdirectories to restore the metadata (it does not matter which one, since each subdirectory contains a complete copy of the metadata), then to each of the subdirectories in turn to restore the data. Suppose that we want to restore the backup having backup ID 100 that was taken with four LDMs, and that the BackupDataDir is /opt. To restore the metadata in this case, we can invoke ndb_restore like this:

shell> ndb_restore -n 1 -b 1 -m --backup-path=opt/BACKUP/BACKUP-100/BACKUP-100-PART-1-OF-4

To restore the table data, execute ndb_restore four times, each time using one of the subdirectories in turn, as shown here:

shell> ndb_restore -n 1 -b 1 -r --backup-path=opt/BACKUP/BACKUP-100/BACKUP-100-PART-1-OF-4
shell> ndb_restore -n 1 -b 1 -r --backup-path=opt/BACKUP/BACKUP-100/BACKUP-100-PART-2-OF-4
shell> ndb_restore -n 1 -b 1 -r --backup-path=opt/BACKUP/BACKUP-100/BACKUP-100-PART-3-OF-4
shell> ndb_restore -n 1 -b 1 -r --backup-path=opt/BACKUP/BACKUP-100/BACKUP-100-PART-4-OF-4

You can employ the same technique to restore a parallel backup to an older version of NDB Cluster (prior to NDB 8.0.16) that does not support parallel backups, using the ndb_restore binary supplied with the older version of the NDB Cluster software.

23.4.24 ndb_select_all — Print Rows from an NDB Table

ndb_select_all prints all rows from an NDB table to stdout.

Usage

ndb_select_all -c connection_string tbl_name -d db_name [> file_name]

The following table includes options that are specific to the NDB Cluster native backup restoration program ndb_select_all. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_select_all), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.43 Command-line options for the ndb_select_all program

Format Description Added, Deprecated, or Removed

--database=dbname,

-d

Name of database in which table is found

(Supported in all MySQL 8.0 based releases)

--parallelism=#,

-p

Degree of parallelism

(Supported in all MySQL 8.0 based releases)

--lock=#,

-l

Lock type

(Supported in all MySQL 8.0 based releases)

--order=index,

-o

Sort resultset according to index having this name

(Supported in all MySQL 8.0 based releases)

--descending,

-z

Sort resultset in descending order (requires --order)

(Supported in all MySQL 8.0 based releases)

--header,

-h

Print header (set to 0|FALSE to disable headers in output)

(Supported in all MySQL 8.0 based releases)

--useHexFormat,

-x

Output numbers in hexadecimal format

(Supported in all MySQL 8.0 based releases)

--delimiter=char,

-D

Set column delimiter

(Supported in all MySQL 8.0 based releases)

--disk

Print disk references (useful only for Disk Data tables having nonindexed columns)

(Supported in all MySQL 8.0 based releases)

--rowid

Print row ID

(Supported in all MySQL 8.0 based releases)

--gci

Include GCI in output

(Supported in all MySQL 8.0 based releases)

--gci64

Include GCI and row epoch in output

(Supported in all MySQL 8.0 based releases)

--tupscan,

-t

Scan in tup order

(Supported in all MySQL 8.0 based releases)

--nodata

Do not print table column data

(Supported in all MySQL 8.0 based releases)


  • --database=dbname, -d dbname

    Name of the database in which the table is found. The default value is TEST_DB.

  • parallelism=#, -p #

    Specifies the degree of parallelism.

  • --lock=lock_type, -l lock_type

    Employs a lock when reading the table. Possible values for lock_type are:

    • 0: Read lock

    • 1: Read lock with hold

    • 2: Exclusive read lock

    There is no default value for this option.

  • --order=index_name, -o index_name

    Orders the output according to the index named index_name.

    Note

    This is the name of an index, not of a column; the index must have been explicitly named when created.

  • --descending, -z

    Sorts the output in descending order. This option can be used only in conjunction with the -o (--order) option.

  • --header=FALSE

    Excludes column headers from the output.

  • --useHexFormat -x

    Causes all numeric values to be displayed in hexadecimal format. This does not affect the output of numerals contained in strings or datetime values.

  • --delimiter=character, -D character

    Causes the character to be used as a column delimiter. Only table data columns are separated by this delimiter.

    The default delimiter is the tab character.

  • --disk

    Adds a disk reference column to the output. The column is nonempty only for Disk Data tables having nonindexed columns.

  • --rowid

    Adds a ROWID column providing information about the fragments in which rows are stored.

  • --gci

    Adds a GCI column to the output showing the global checkpoint at which each row was last updated. See Section 23.1, “NDB Cluster Overview”, and Section 23.5.3.2, “NDB Cluster Log Events”, for more information about checkpoints.

  • --gci64

    Adds a ROW$GCI64 column to the output showing the global checkpoint at which each row was last updated, as well as the number of the epoch in which this update occurred.

  • --tupscan, -t

    Scan the table in the order of the tuples.

  • --nodata

    Causes any table data to be omitted.

Sample Output

Output from a MySQL SELECT statement:

mysql> SELECT * FROM ctest1.fish;
+----+-----------+
| id | name      |
+----+-----------+
|  3 | shark     |
|  6 | puffer    |
|  2 | tuna      |
|  4 | manta ray |
|  5 | grouper   |
|  1 | guppy     |
+----+-----------+
6 rows in set (0.04 sec)

Output from the equivalent invocation of ndb_select_all:

shell> ./ndb_select_all -c localhost fish -d ctest1
id      name
3       [shark]
6       [puffer]
2       [tuna]
4       [manta ray]
5       [grouper]
1       [guppy]
6 rows returned

NDBT_ProgramExit: 0 - OK

All string values are enclosed by square brackets ([...]) in the output of ndb_select_all. For another example, consider the table created and populated as shown here:

CREATE TABLE dogs (
    id INT(11) NOT NULL AUTO_INCREMENT,
    name VARCHAR(25) NOT NULL,
    breed VARCHAR(50) NOT NULL,
    PRIMARY KEY pk (id),
    KEY ix (name)
)
TABLESPACE ts STORAGE DISK
ENGINE=NDBCLUSTER;

INSERT INTO dogs VALUES
    ('', 'Lassie', 'collie'),
    ('', 'Scooby-Doo', 'Great Dane'),
    ('', 'Rin-Tin-Tin', 'Alsatian'),
    ('', 'Rosscoe', 'Mutt');

This demonstrates the use of several additional ndb_select_all options:

shell> ./ndb_select_all -d ctest1 dogs -o ix -z --gci --disk
GCI     id name          breed        DISK_REF
834461  2  [Scooby-Doo]  [Great Dane] [ m_file_no: 0 m_page: 98 m_page_idx: 0 ]
834878  4  [Rosscoe]     [Mutt]       [ m_file_no: 0 m_page: 98 m_page_idx: 16 ]
834463  3  [Rin-Tin-Tin] [Alsatian]   [ m_file_no: 0 m_page: 34 m_page_idx: 0 ]
835657  1  [Lassie]      [Collie]     [ m_file_no: 0 m_page: 66 m_page_idx: 0 ]
4 rows returned

NDBT_ProgramExit: 0 - OK

23.4.25 ndb_select_count — Print Row Counts for NDB Tables

ndb_select_count prints the number of rows in one or more NDB tables. With a single table, the result is equivalent to that obtained by using the MySQL statement SELECT COUNT(*) FROM tbl_name.

Usage

ndb_select_count [-c connection_string] -ddb_name tbl_name[, tbl_name2[, ...]]

The following table includes options that are specific to the NDB Cluster native backup restoration program ndb_select_count. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_select_count), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.44 Command-line options for the ndb_select_count program

Format Description Added, Deprecated, or Removed

--database=dbname,

-d

Name of database in which table is found

(Supported in all MySQL 8.0 based releases)

--parallelism=#,

-p

Degree of parallelism

(Supported in all MySQL 8.0 based releases)

--lock=#,

-l

Lock type

(Supported in all MySQL 8.0 based releases)


You can obtain row counts from multiple tables in the same database by listing the table names separated by spaces when invoking this command, as shown under Sample Output.

Sample Output

shell> ./ndb_select_count -c localhost -d ctest1 fish dogs
6 records in table fish
4 records in table dogs

NDBT_ProgramExit: 0 - OK

23.4.26 ndb_setup.py — Start browser-based Auto-Installer for NDB Cluster (DEPRECATED)

Note

This feature is deprecated and should be avoided. It is subject to removal in a future version of NDB Cluster.

ndb_setup.py starts the NDB Cluster Auto-Installer and opens the installer's Start page in the default Web browser.

Important

This program is intended to be invoked as a normal user, and not with the mysql, system root or other administrative account.

This section describes usage of and program options for the command-line tool only. For information about using the Auto-Installer GUI that is spawned when ndb_setup.py is invoked, see The NDB Cluster Auto-Installer (NDB 7.5) (No longer supported).

Usage

All platforms:

ndb_setup.py [options]

Additionally, on Windows platforms only:

setup.bat [options]

The following table includes all options that are supported by the NDB Cluster installation and configuration program ndb_setup.py. Additional descriptions follow the table.

Table 23.45 Command-line options for the ndb_setup.py program

Format Description Added, Deprecated, or Removed

--browser-start-page=filename,

-s

Page that web browser opens when starting

(Supported in all MySQL 8.0 based releases)

--ca-certs-file=filename,

-a

File containing list of client certificates allowed to connect to server

(Supported in all MySQL 8.0 based releases)

--cert-file=filename,

-c

File containing X509 certificate identifying server

(Supported in all MySQL 8.0 based releases)

--debug-level=level,

-d

Python logging module debug level; one of DEBUG, INFO, WARNING (default), ERROR, or CRITICAL

(Supported in all MySQL 8.0 based releases)

--help,

-h

Print help message

(Supported in all MySQL 8.0 based releases)

--key-file=file,

-k

Specify file containing private key (if not included in --cert-file)

(Supported in all MySQL 8.0 based releases)

--no-browser,

-n

Do not open start page in browser, merely start tool

(Supported in all MySQL 8.0 based releases)

--port=#,

-p

Specify port used by web server

(Supported in all MySQL 8.0 based releases)

--server-log-file=file,

-o

Log requests to this file; use '-' to force logging to stderr instead

(Supported in all MySQL 8.0 based releases)

--server-name=name,

-N

Name of server to connect to

(Supported in all MySQL 8.0 based releases)

--use-http,

-H

Use unencrypted (HTTP) client/server connection

(Supported in all MySQL 8.0 based releases)

--use-https,

-S

Use encrypted (HTTPS) client/server connection

(Supported in all MySQL 8.0 based releases)


  • --browser-start-page=file, -s

    Command-Line Format --browser-start-page=filename
    Type String
    Default Value index.html

    Specify the file to open in the browser as the installation and configuration Start page. The default is index.html.

  • --ca-certs-file=file, -a

    Command-Line Format --ca-certs-file=filename
    Type File name
    Default Value [none]

    Specify a file containing a list of client certificates which are allowed to connect to the server. The default is an empty string, which means that no client authentication is used.

  • --cert-file=file, -c

    Command-Line Format --cert-file=filename
    Type File name
    Default Value /usr/share/mysql/mcc/cfg.pem

    Specify a file containing an X509 certificate which identifies the server. It is possible for the certificate to be self-signed. The default is cfg.pem.

  • --debug-level=level, -d

    Command-Line Format --debug-level=level
    Type Enumeration
    Default Value WARNING
    Valid Values

    WARNING

    DEBUG

    INFO

    ERROR

    CRITICAL

    Set the Python logging module debug level. This is one of DEBUG, INFO, WARNING, ERROR, or CRITICAL. WARNING is the default.

  • --help, -h

    Command-Line Format --help

    Print a help message.

  • --key-file=file, -d

    Command-Line Format --key-file=file
    Type File name
    Default Value [none]

    Specify a file containing the private key if this is not included in the X509 certificate file (--cert-file). The default is an empty string, which means that no such file is used.

  • --no-browser, -n

    Command-Line Format --no-browser

    Start the installation and configuration tool, but do not open the Start page in a browser.

  • --port=#, -p

    Command-Line Format --port=#
    Type Numeric
    Default Value 8081
    Minimum Value 1
    Maximum Value 65535

    Set the port used by the web server. The default is 8081.

  • --server-log-file=file, -o

    Command-Line Format --server-log-file=file
    Type File name
    Default Value ndb_setup.log
    Valid Values

    ndb_setup.log

    - (Log to stderr)

    Log requests to this file. The default is ndb_setup.log. To specify logging to stderr, rather than to a file, use a - (dash character) for the file name.

  • --server-name=host, -N

    Command-Line Format --server-name=name
    Type String
    Default Value localhost

    Specify the host name or IP address for the browser to use when connecting. The default is localhost.

  • --use-http, -H

    Command-Line Format --use-http

    Make the browser use HTTP to connect with the server. This means that the connection is unencrypted and not secured in any way.

  • --use-https, -S

    Command-Line Format --use-https

    Make the browser use a secure (HTTPS) connection with the server.

23.4.27 ndb_show_tables — Display List of NDB Tables

ndb_show_tables displays a list of all NDB database objects in the cluster. By default, this includes not only both user-created tables and NDB system tables, but NDB-specific indexes, internal triggers, and NDB Cluster Disk Data objects as well.

The following table includes options that are specific to the NDB Cluster native backup restoration program ndb_show_tables. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_show_tables), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.46 Command-line options for the ndb_show_tables program

Format Description Added, Deprecated, or Removed

--database=string,

-d

Specifies database in which table is found; database name must be followed by table name

(Supported in all MySQL 8.0 based releases)

--loops=#,

-l

Number of times to repeat output

(Supported in all MySQL 8.0 based releases)

--parsable,

-p

Return output suitable for MySQL LOAD DATA statement

(Supported in all MySQL 8.0 based releases)

--show-temp-status

Show table temporary flag

(Supported in all MySQL 8.0 based releases)

--type=#,

-t

Limit output to objects of this type

(Supported in all MySQL 8.0 based releases)

--unqualified,

-u

Do not qualify table names

(Supported in all MySQL 8.0 based releases)


Usage

ndb_show_tables [-c connection_string]
  • --database, -d

    Specifies the name of the database in which the desired table is found. If this option is given, the name of a table must follow the database name.

    If this option has not been specified, and no tables are found in the TEST_DB database, ndb_show_tables issues a warning.

  • --loops, -l

    Specifies the number of times the utility should execute. This is 1 when this option is not specified, but if you do use the option, you must supply an integer argument for it.

  • --parsable, -p

    Using this option causes the output to be in a format suitable for use with LOAD DATA.

  • --show-temp-status

    If specified, this causes temporary tables to be displayed.

  • --type, -t

    Can be used to restrict the output to one type of object, specified by an integer type code as shown here:

    • 1: System table

    • 2: User-created table

    • 3: Unique hash index

    Any other value causes all NDB database objects to be listed (the default).

  • --unqualified, -u

    If specified, this causes unqualified object names to be displayed.

Note

Only user-created NDB Cluster tables may be accessed from MySQL; system tables such as SYSTAB_0 are not visible to mysqld. However, you can examine the contents of system tables using NDB API applications such as ndb_select_all (see Section 23.4.24, “ndb_select_all — Print Rows from an NDB Table”).

Prior to NDB 8.0.20, this program printed NDBT_ProgramExit - status upon completion of its run, due to an unnecessary dependency on the NDBT testing library. This dependency has been removed, eliminating the extraneous output.

23.4.28 ndb_size.pl — NDBCLUSTER Size Requirement Estimator

This is a Perl script that can be used to estimate the amount of space that would be required by a MySQL database if it were converted to use the NDBCLUSTER storage engine. Unlike the other utilities discussed in this section, it does not require access to an NDB Cluster (in fact, there is no reason for it to do so). However, it does need to access the MySQL server on which the database to be tested resides.

Requirements

  • A running MySQL server. The server instance does not have to provide support for NDB Cluster.

  • A working installation of Perl.

  • The DBI module, which can be obtained from CPAN if it is not already part of your Perl installation. (Many Linux and other operating system distributions provide their own packages for this library.)

  • A MySQL user account having the necessary privileges. If you do not wish to use an existing account, then creating one using GRANT USAGE ON db_name.*—where db_name is the name of the database to be examined—is sufficient for this purpose.

ndb_size.pl can also be found in the MySQL sources in storage/ndb/tools.

The following table includes options that are specific to the NDB Cluster program ndb_size.pl. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_size.pl), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.47 Command-line options for the ndb_size.pl program

Format Description Added, Deprecated, or Removed

--database=dbname

Database or databases to examine; a comma-delimited list; default is ALL (use all databases found on server)

(Supported in all MySQL 8.0 based releases)

--hostname[:port]

Specify host and optional port as host[:port]

(Supported in all MySQL 8.0 based releases)

--socket=file_name

Specify socket to connect to

(Supported in all MySQL 8.0 based releases)

--user=string

Specify MySQL user name

(Supported in all MySQL 8.0 based releases)

--password=string

Specify MySQL user password

(Supported in all MySQL 8.0 based releases)

--format=string

Set output format (text or HTML)

(Supported in all MySQL 8.0 based releases)

--excludetables=tbl_list

Skip any tables in comma-separated list

(Supported in all MySQL 8.0 based releases)

--excludedbs=db_list

Skip any databases in comma-separated list

(Supported in all MySQL 8.0 based releases)

--savequeries=file

Saves all queries on database into file specified

(Supported in all MySQL 8.0 based releases)

--loadqueries=file

Loads all queries from file specified; does not connect to database

(Supported in all MySQL 8.0 based releases)

--real_table_name=table

Designates table to handle unique index size calculations

(Supported in all MySQL 8.0 based releases)


Usage

perl ndb_size.pl [--database={db_name|ALL}] [--hostname=host[:port]] [--socket=socket] \
      [--user=user] [--password=password]  \
      [--help|-h] [--format={html|text}] \
      [--loadqueries=file_name] [--savequeries=file_name]

By default, this utility attempts to analyze all databases on the server. You can specify a single database using the --database option; the default behavior can be made explicit by using ALL for the name of the database. You can also exclude one or more databases by using the --excludedbs option with a comma-separated list of the names of the databases to be skipped. Similarly, you can cause specific tables to be skipped by listing their names, separated by commas, following the optional --excludetables option. A host name can be specified using --hostname; the default is localhost. You can specify a port in addition to the host using host:port format for the value of --hostname. The default port number is 3306. If necessary, you can also specify a socket; the default is /var/lib/mysql.sock. A MySQL user name and password can be specified the corresponding options shown. It also possible to control the format of the output using the --format option; this can take either of the values html or text, with text being the default. An example of the text output is shown here:

shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock
ndb_size.pl report for database: 'test' (1 tables)
--------------------------------------------------
Connected to: DBI:mysql:host=localhost;mysql_socket=/tmp/mysql.sock

Including information for versions: 4.1, 5.0, 5.1

test.t1
-------

DataMemory for Columns (* means varsized DataMemory):
         Column Name            Type  Varsized   Key  4.1  5.0   5.1
     HIDDEN_NDB_PKEY          bigint             PRI    8    8     8
                  c2     varchar(50)         Y         52   52    4*
                  c1         int(11)                    4    4     4
                                                       --   --    --
Fixed Size Columns DM/Row                              64   64    12
   Varsize Columns DM/Row                               0    0     4

DataMemory for Indexes:
   Index Name                 Type        4.1        5.0        5.1
      PRIMARY                BTREE         16         16         16
                                           --         --         --
       Total Index DM/Row                  16         16         16

IndexMemory for Indexes:
               Index Name        4.1        5.0        5.1
                  PRIMARY         33         16         16
                                  --         --         --
           Indexes IM/Row         33         16         16

Summary (for THIS table):
                                 4.1        5.0        5.1
    Fixed Overhead DM/Row         12         12         16
           NULL Bytes/Row          4          4          4
           DataMemory/Row         96         96         48
                    (Includes overhead, bitmap and indexes)

  Varsize Overhead DM/Row          0          0          8
   Varsize NULL Bytes/Row          0          0          4
       Avg Varside DM/Row          0          0         16

                 No. Rows          0          0          0

        Rows/32kb DM Page        340        340        680
Fixedsize DataMemory (KB)          0          0          0

Rows/32kb Varsize DM Page          0          0       2040
  Varsize DataMemory (KB)          0          0          0

         Rows/8kb IM Page        248        512        512
         IndexMemory (KB)          0          0          0

Parameter Minimum Requirements
------------------------------
* indicates greater than default

                Parameter     Default        4.1         5.0         5.1
          DataMemory (KB)       81920          0           0           0
       NoOfOrderedIndexes         128          1           1           1
               NoOfTables         128          1           1           1
         IndexMemory (KB)       18432          0           0           0
    NoOfUniqueHashIndexes          64          0           0           0
           NoOfAttributes        1000          3           3           3
             NoOfTriggers         768          5           5           5

For debugging purposes, the Perl arrays containing the queries run by this script can be read from the file specified using can be saved to a file using --savequeries; a file containing such arrays to be read during script execution can be specified using --loadqueries. Neither of these options has a default value.

To produce output in HTML format, use the --format option and redirect the output to a file, as shown here:

shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock --format=html > ndb_size.html

(Without the redirection, the output is sent to stdout.)

The output from this script includes the following information:

23.4.29 ndb_top — View CPU usage information for NDB threads

ndb_top displays running information in the terminal about CPU usage by NDB threads on an NDB Cluster data node. Each thread is represented by two rows in the output, the first showing system statistics, the second showing the measured statistics for the thread.

ndb_top is available beginning with MySQL NDB Cluster 7.6.3.

Usage

ndb_top [-h hostname] [-t port] [-u user] [-p pass] [-n node_id]

ndb_top connects to a MySQL Server running as an SQL node of the cluster. By default, it attempts to connect to a mysqld running on localhost and port 3306, as the MySQL root user with no password specified. You can override the default host and port using, respectively, --host (-h) and --port (-t). To specify a MySQL user and password, use the --user (-u) and --passwd (-p) options. This user must be able to read tables in the ndbinfo database (ndb_top uses information from ndbinfo.cpustat and related tables).

For more information about MySQL user accounts and passwords, see Section 6.2, “Access Control and Account Management”.

Output is available as plain text or an ASCII graph; you can specify this using the --text (-x) and --graph (-g) options, respectively. These two display modes provide the same information; they can be used concurrently. At least one display mode must be in use.

Color display of the graph is supported and enabled by default (--color or -c option). With color support enabled, the graph display shows OS user time in blue, OS system time in green, and idle time as blank. For measured load, blue is used for execution time, yellow for send time, red for time spent in send buffer full waits, and blank spaces for idle time. The percentage shown in the graph display is the sum of percentages for all threads which are not idle. Colors are not currently configurable; you can use grayscale instead by using --skip-color.

The sorted view (--sort, -r) is based on the maximum of the measured load and the load reported by the OS. Display of these can be enabled and disabled using the --measured-load (-m) and --os-load (-o) options. Display of at least one of these loads must be enabled.

The program tries to obtain statistics from a data node having the node ID given by the --node-id (-n) option; if unspecified, this is 1. ndb_top cannot provide information about other types of nodes.

The view adjusts itself to the height and width of the terminal window; the minimum supported width is 76 characters.

Once started, ndb_top runs continuously until forced to exit; you can quit the program using Ctrl-C. The display updates once per second; to set a different delay interval, use --sleep-time (-s).

Note

ndb_top is available on macOS, Linux, and Solaris. It is not currently supported on Windows platforms.

The following table includes all options that are specific to the NDB Cluster program ndb_top. Additional descriptions follow the table.

Table 23.48 Command-line options for the ndb_top program

Format Description Added, Deprecated, or Removed

--color,

-c

Show ASCII graphs in color; use --skip-colors to disable

(Supported in all MySQL 8.0 based releases)

--graph,

-g

Display data using graphs; use --skip-graphs to disable

(Supported in all MySQL 8.0 based releases)

--help,

-?

Show program usage information

(Supported in all MySQL 8.0 based releases)

--host[=name],

-h

Host name or IP address of MySQL Server to connect to

(Supported in all MySQL 8.0 based releases)

--measured-load,

-m

Show measured load by thread

(Supported in all MySQL 8.0 based releases)

--node-id[=#],

-n

Watch node having this node ID

(Supported in all MySQL 8.0 based releases)

--os-load,

-o

Show load measured by operating system

(Supported in all MySQL 8.0 based releases)

--password[=password],

-p

Connect using this password

(Supported in all MySQL 8.0 based releases)

--port[=#],

-P (>=7.6.6)

Port number to use when connecting to MySQL Server

(Supported in all MySQL 8.0 based releases)

--sleep-time[=seconds],

-s

Time to wait between display refreshes, in seconds

(Supported in all MySQL 8.0 based releases)

--socket,

-S

Socket file to use for connection

(Supported in all MySQL 8.0 based releases)

--sort,

-r

Sort threads by usage; use --skip-sort to disable

(Supported in all MySQL 8.0 based releases)

--text,

-t (>=7.6.6)

Display data using text

(Supported in all MySQL 8.0 based releases)

--user[=name],

-u

Connect as this MySQL user

(Supported in all MySQL 8.0 based releases)


In NDB 7.6.6 and later, ndb_top also supports the common NDB program options --defaults-file, --defaults-extra-file, --print-defaults, --no-defaults, and --defaults-group-suffix. (Bug #86614, Bug #26236298)

Additional Options

  • --color, -c

    Command-Line Format --color
    Type Boolean
    Default Value TRUE

    Show ASCII graphs in color; use --skip-colors to disable.

  • --graph, -g

    Command-Line Format --graph
    Type Boolean
    Default Value TRUE

    Display data using graphs; use --skip-graphs to disable. This option or --text must be true; both options may be true.

  • --help, -?

    Command-Line Format --help
    Type Boolean
    Default Value TRUE

    Show program usage information.

  • --host[=name], -h

    Command-Line Format --host[=name]
    Type String
    Default Value localhost

    Host name or IP address of MySQL Server to connect to.

  • --measured-load, -m

    Command-Line Format --measured-load
    Type Boolean
    Default Value FALSE

    Show measured load by thread. This option or --os-load must be true; both options may be true.

  • --node-id[=#], -n

    Command-Line Format --node-id[=#]
    Type Integer
    Default Value 1

    Watch the data node having this node ID.

  • --os-load, -o

    Command-Line Format --os-load
    Type Boolean
    Default Value TRUE

    Show load measured by operating system. This option or --measured-load must be true; both options may be true.

  • --passwd[=password], -p

    Command-Line Format --passwd[=password]
    Type Boolean
    Default Value NULL

    Connect using this password.

    This option is deprecated in NDB 7.6.4. It is removed in NDB 7.6.6, where it is replaced by the --password option. (Bug #26907833)

  • --password[=password], -p

    Command-Line Format --password[=password]
    Type Boolean
    Default Value NULL

    Connect using this password.

    This option was added in NDB 7.6.6 as a replacement for the --passwd option used previously. (Bug #26907833)

  • --port[=#], -t (NDB 7.6.6 and later: -P)

    Command-Line Format --port[=#]
    Type Integer
    Default Value 3306

    Port number to use when connecting to MySQL Server.

    Beginning with NDB 7.6.6, the short form for this option is -P, and -t is repurposed as the short form for the --text option. (Bug #26907833)

  • --sleep-time[=seconds], -s

    Command-Line Format --sleep-time[=seconds]
    Type Integer
    Default Value 1

    Time to wait between display refreshes, in seconds.

  • --socket=path/to/file, -S

    Command-Line Format --socket
    Type Path name
    Default Value [none]

    Use the specified socket file for the connection.

    Added in NDB 7.6.6. (Bug #86614, Bug #26236298)

  • --sort, -r

    Command-Line Format --sort
    Type Boolean
    Default Value TRUE

    Sort threads by usage; use --skip-sort to disable.

  • --text, -t

    Command-Line Format --text
    Type Boolean
    Default Value FALSE

    Display data using text. This option or --graph must be true; both options may be true.

    The short form for this option was -x in previous versions of NDB Cluster, but this is no longer supported.

  • --user[=name], -u

    Command-Line Format --user[=name]
    Type String
    Default Value root

    Connect as this MySQL user.

Sample Output.  The next figure shows ndb_top running in a terminal window on a Linux system with an ndbmtd data node under a moderate load. Here, the program has been invoked using ndb_top -n8 -x to provide both text and graph output:

Figure 23.26 ndb_top Running in Terminal

Display from ndb_top, running in a terminal window. Shows information for each node, including the utilized resources.

Beginning with NDB 8.0.20, ndb_top also shows spin times for threads, displayed in green.

23.4.30 ndb_waiter — Wait for NDB Cluster to Reach a Given Status

ndb_waiter repeatedly (each 100 milliseconds) prints out the status of all cluster data nodes until either the cluster reaches a given status or the --timeout limit is exceeded, then exits. By default, it waits for the cluster to achieve STARTED status, in which all nodes have started and connected to the cluster. This can be overridden using the --no-contact and --not-started options.

The node states reported by this utility are as follows:

  • NO_CONTACT: The node cannot be contacted.

  • UNKNOWN: The node can be contacted, but its status is not yet known. Usually, this means that the node has received a START or RESTART command from the management server, but has not yet acted on it.

  • NOT_STARTED: The node has stopped, but remains in contact with the cluster. This is seen when restarting the node using the management client's RESTART command.

  • STARTING: The node's ndbd process has started, but the node has not yet joined the cluster.

  • STARTED: The node is operational, and has joined the cluster.

  • SHUTTING_DOWN: The node is shutting down.

  • SINGLE USER MODE: This is shown for all cluster data nodes when the cluster is in single user mode.

The following table includes options that are specific to the NDB Cluster native backup restoration program ndb_waiter. Additional descriptions follow the table. For options common to most NDB Cluster programs (including ndb_waiter), see Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”.

Table 23.49 Command-line options for the ndb_waiter program

Format Description Added, Deprecated, or Removed

--no-contact,

-n

Wait for cluster to reach NO CONTACT state

(Supported in all MySQL 8.0 based releases)

--not-started

Wait for cluster to reach NOT STARTED state

(Supported in all MySQL 8.0 based releases)

--single-user

Wait for cluster to enter single user mode

(Supported in all MySQL 8.0 based releases)

--timeout=#,

-t

Wait this many seconds, then exit whether or not cluster has reached desired state

(Supported in all MySQL 8.0 based releases)

--nowait-nodes=list

List of nodes not to be waited for

(Supported in all MySQL 8.0 based releases)

--wait-nodes=list,

-w

List of nodes to be waited for

(Supported in all MySQL 8.0 based releases)


Usage

ndb_waiter [-c connection_string]

Additional Options

  • --no-contact, -n

    Instead of waiting for the STARTED state, ndb_waiter continues running until the cluster reaches NO_CONTACT status before exiting.

  • --not-started

    Instead of waiting for the STARTED state, ndb_waiter continues running until the cluster reaches NOT_STARTED status before exiting.

  • --timeout=seconds, -t seconds

    Time to wait. The program exits if the desired state is not achieved within this number of seconds. The default is 120 seconds (1200 reporting cycles).

  • --single-user

    The program waits for the cluster to enter single user mode.

  • --nowait-nodes=list

    When this option is used, ndb_waiter does not wait for the nodes whose IDs are listed. The list is comma-delimited; ranges can be indicated by dashes, as shown here:

    shell> ndb_waiter --nowait-nodes=1,3,7-9
    
    Important

    Do not use this option together with the --wait-nodes option.

  • --wait-nodes=list, -w list

    When this option is used, ndb_waiter waits only for the nodes whose IDs are listed. The list is comma-delimited; ranges can be indicated by dashes, as shown here:

    shell> ndb_waiter --wait-nodes=2,4-6,10
    
    Important

    Do not use this option together with the --nowait-nodes option.

Sample Output.  Shown here is the output from ndb_waiter when run against a 4-node cluster in which two nodes have been shut down and then started again manually. Duplicate reports (indicated by ...) are omitted.

shell> ./ndb_waiter -c localhost

Connecting to mgmsrv at (localhost)
State node 1 STARTED
State node 2 NO_CONTACT
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 UNKNOWN
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 NO_CONTACT
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 UNKNOWN
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 STARTING
State node 3 STARTED
State node 4 STARTING
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 STARTED
State node 3 STARTED
State node 4 STARTING
Waiting for cluster enter state STARTED

...

State node 1 STARTED
State node 2 STARTED
State node 3 STARTED
State node 4 STARTED
Waiting for cluster enter state STARTED
Note

If no connection string is specified, then ndb_waiter tries to connect to a management on localhost, and reports Connecting to mgmsrv at (null).

Prior to NDB 8.0.20, this program printed NDBT_ProgramExit - status upon completion of its run, due to an unnecessary dependency on the NDBT testing library. This dependency has been removed, eliminating the extraneous output.

23.4.31 ndbxfrm — Compress, Decompress, Encrypt, and Decrypt Files Created by NDB Cluster

The ndbxfrm utility, introduced in NDB 8.0.22, can be used to decompress, decrypt, and output information about files created by NDB Cluster that are compressed, encrypted, or both. It can also be used to compress or encrypt files.

Table 23.50 Command-line options for the ndbxfrm program

Format Description Added, Deprecated, or Removed

--compress,

-c

Compress file

ADDED: NDB 8.0.22

--decrypt-password=string

Use this password to decrypt file

ADDED: NDB 8.0.22

--encrypt-kdf-iter-count=#,

-k

Number of iterations used in key definition

ADDED: NDB 8.0.22

--encrypt-password=string

Use this password to encrypt file

ADDED: NDB 8.0.22

--help,

-?

Print usage information

ADDED: NDB 8.0.22

--info,

-i

Print file information

ADDED: NDB 8.0.22

--usage,

-?

Prints usage information; synonym for --help

ADDED: NDB 8.0.22

--version,

-V

Output version information

ADDED: NDB 8.0.22


Usage

ndbxfrm --info file[ file ...]

ndbxfrm --compress input_file output_file

ndbxfrm --decrypt-password=password input_file output_file

ndbxfrm [--encrypt-ldf-iter-count=#] --encrypt-password=password input_file output_file

input_file and output_file cannot be the same file.

Options

  • --compress, -c

    Compresses the input file, using the same compression method as is used for compressing NDB Cluster backups, and writes the output to an output file. To decompress a compressed NDB backup file that is not encrypted, it is necessary only to invoke ndbxfrm using the names of the compressed file and an output file (with no options required).

  • --decrypt-password=password

    Decrypts a file encrypted by NDB using the password supplied.

  • --encrypt-kdf-iter-count=#, -k #

    When encrypting a file, specifies the number of iterations to use for the encryption key. Requires the --encrypt-password option.

  • --encrypt-password=password

    Encrypts the backup file using the password supplied by the option. The password must meet the requirements listed here:

    • Uses any of the printable ASCII characters except !, ', ", $, %, \, and ^

    • Is no more than 256 characters in length

    • Is enclosed by single or double quotation marks

    It is possible but not recommended to use an empty password ('' or "").

  • --help, -?

    Prints usage information for the program.

  • --info, -i

    Prints the following information about one or more input files:

    • The name of the file

    • Whether the file is compressed (compression=yes or compression=no)

    • Whether the file is encrypted (encryption=yes or encryption=no)

    Example:

    shell> ndbxfrm -i BACKUP-10-0.5.Data BACKUP-10.5.ctl BACKUP-10.5.log
    File=BACKUP-10-0.5.Data, compression=no, encryption=yes
    File=BACKUP-10.5.ctl, compression=no, encryption=yes
    File=BACKUP-10.5.log, compression=no, encryption=yes
    
  • --usage, -?

    Synonym for --help.

  • --version, -V

    Prints out version information.

ndbxfrm can encrypt backups created by any version of NDB Cluster. The .Data, .ctl, and .log files comprising the backup must be encrypted separately, and these files must be encrypted separately for each data node. Once encrypted, such backups can be decrypted only by ndbxfrm, ndb_restore, or ndb_print_backup from NDB Cluster 8.0.22 or later.

An encrypted file can be re-encrypted with a new password using the --encrypt-password and --decrypt-password options together, like this:

ndbxfrm --decrypt-password=old --encrypt-password=new input_file output_file

In the example just shown, old and new are the old and new passwords, respectively; both of these must be quoted. The input file is decrypted and then encrypted as the output file. The input file itself is not changed; if you do not want it to be accessible using the old password, you must remove the input file manually.

ndbxfrm does not take any of the options shown in Section 23.4.32, “Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs”, other than those explicitly listed in this section (that is, --help, --usage, and --version).

23.4.32 Options Common to NDB Cluster Programs — Options Common to NDB Cluster Programs

All NDB Cluster programs accept the options described in this section, with the following exceptions:

Note

Users of earlier NDB Cluster versions should note that some of these options have been changed to make them consistent with one another, and also with mysqld. You can use the --help option with any NDB Cluster program—with the exception of ndb_print_backup_file, ndb_print_schema_file, and ndb_print_sys_file—to view a list of the options which the program supports.

The options in the following table are common to all NDB Cluster executables (except those noted previously in this section).

Table 23.51 Command-line options common to all MySQL NDB Cluster programs

Format Description Added, Deprecated, or Removed

--character-sets-dir=dir_name

Directory where character sets are installed

(Supported in all MySQL 8.0 based releases)

--connect-retries=#

Set the number of times to retry a connection before giving up

(Supported in all MySQL 8.0 based releases)

--connect-retry-delay=#

Time to wait between attempts to contact a management server, in seconds

(Supported in all MySQL 8.0 based releases)

--core-file

Write core on errors (defaults to TRUE in debug builds)

(Supported in all MySQL 8.0 based releases)

--debug=options

Enable output from debug calls. Can be used only for versions compiled with debugging enabled

(Supported in all MySQL 8.0 based releases)

--defaults-extra-file=filename

Read this file after global option files are read

(Supported in all MySQL 8.0 based releases)

--defaults-file=filename

Read default options from this file

(Supported in all MySQL 8.0 based releases)

--defaults-group-suffix

Also read groups with names ending in this suffix

(Supported in all MySQL 8.0 based releases)

--help,

--usage,

-?

Display help message and exit

(Supported in all MySQL 8.0 based releases)

--login-path=path

Read this path from the login file

(Supported in all MySQL 8.0 based releases)

--ndb-connectstring=connectstring,

--connect-string=connectstring,

-c

Set connection string for connecting to ndb_mgmd. Syntax: [nodeid=<id>;][host=]<hostname>[:<port>]. Overrides entries specified in NDB_CONNECTSTRING or my.cnf

(Supported in all MySQL 8.0 based releases)

--ndb-mgmd-host=host[:port]

Set the host (and port, if desired) for connecting to management server

(Supported in all MySQL 8.0 based releases)

--ndb-nodeid=#

Set node id for this node

(Supported in all MySQL 8.0 based releases)

--ndb-optimized-node-selection

Select nodes for transactions in a more optimal way

(Supported in all MySQL 8.0 based releases)

--no-defaults

Do not read default options from any option file other than login file

(Supported in all MySQL 8.0 based releases)

--print-defaults

Print the program argument list and exit

(Supported in all MySQL 8.0 based releases)

--version,

-V

Output version information and exit

(Supported in all MySQL 8.0 based releases)


For options specific to individual NDB Cluster programs, see Section 23.4, “NDB Cluster Programs”.

See Section 23.3.3.9.1, “MySQL Server Options for NDB Cluster”, for mysqld options relating to NDB Cluster.

  • --character-sets-dir=name

    Command-Line Format --character-sets-dir=dir_name
    Type Directory name
    Default Value

    Tells the program where to find character set information.

  • --connect-retries=#

    Command-Line Format --connect-retries=#
    Type Numeric
    Default Value 12
    Minimum Value 0
    Maximum Value 4294967295

    This option specifies the number of times following the first attempt to retry a connection before giving up (the client always tries the connection at least once). The length of time to wait per attempt is set using --connect-retry-delay.

    Note

    When used with ndb_mgm, this option has 3 as its default. See Section 23.4.5, “ndb_mgm — The NDB Cluster Management Client”, for more information.

  • --connect-retry-delay=#

    Command-Line Format --connect-retry-delay=#
    Type Numeric
    Default Value 5
    Minimum Value 1
    Minimum Value 0
    Maximum Value 4294967295

    This option specifies the length of time to wait per attempt a connection before giving up. The number of times to try connecting is set by --connect-retries.

  • --core-file

    Command-Line Format --core-file
    Type Boolean
    Default Value FALSE

    Write a core file if the program dies. The name and location of the core file are system-dependent. (For NDB Cluster programs nodes running on Linux, the default location is the program's working directory—for a data node, this is the node's DataDir.) For some systems, there may be restrictions or limitations. For example, it might be necessary to execute ulimit -c unlimited before starting the server. Consult your system documentation for detailed information.

    If NDB Cluster was built using the --debug option for configure, then --core-file is enabled by default. For regular builds, --core-file is disabled by default.

  • --debug[=options]

    Command-Line Format --debug=options
    Type String
    Default Value d:t:O,/tmp/ndb_restore.trace

    This option can be used only for versions compiled with debugging enabled. It is used to enable output from debug calls in the same manner as for the mysqld process.

  • --defaults-extra-file=filename

    Command-Line Format --defaults-extra-file=filename
    Type String
    Default Value [none]

    Read this file after global option files are read.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --defaults-file=filename

    Command-Line Format --defaults-file=filename
    Type String
    Default Value [none]

    Read default options from this file.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --defaults-group-suffix

    Command-Line Format --defaults-group-suffix
    Type String
    Default Value [none]

    Also read groups with names ending in this suffix.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --help, --usage, -?

    Command-Line Format

    --help

    --usage

    Prints a short list with descriptions of the available command options.

  • --login-path=path

    Command-Line Format --login-path=path
    Type String
    Default Value [none]

    Read this path from the login file.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --ndb-connectstring=connection_string, --connect-string=connection_string, -c connection_string

    Command-Line Format

    --ndb-connectstring=connectstring

    --connect-string=connectstring

    Type String
    Default Value localhost:1186

    This option takes an NDB Cluster connection string that specifies the management server for the application to connect to, as shown here:

    shell> ndbd --ndb-connectstring="nodeid=2;host=ndb_mgmd.mysql.com:1186"
    

    For more information, see Section 23.3.3.3, “NDB Cluster Connection Strings”.

  • --ndb-mgmd-host=host[:port]

    Command-Line Format --ndb-mgmd-host=host[:port]
    Type String
    Default Value localhost:1186

    Can be used to set the host and port number of a single management server for the program to connect to. If the program requires node IDs or references to multiple management servers (or both) in its connection information, use the --ndb-connectstring option instead.

  • --ndb-nodeid=#

    Command-Line Format --ndb-nodeid=#
    Type Numeric
    Default Value 0

    Sets this node's NDB Cluster node ID. The range of permitted values depends on the node's type (data, management, or API) and the NDB Cluster software version. See Section 23.1.7.2, “Limits and Differences of NDB Cluster from Standard MySQL Limits”, for more information.

  • --no-defaults

    Command-Line Format --no-defaults
    Type Boolean
    Default Value TRUE

    Do not read default options from any option file other than login file.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --ndb-optimized-node-selection

    Command-Line Format --ndb-optimized-node-selection
    Type Boolean
    Default Value TRUE

    Optimize selection of nodes for transactions. Enabled by default.

  • --print-defaults

    Command-Line Format --print-defaults
    Type Boolean
    Default Value TRUE

    Print the program argument list and exit.

    For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling”.

  • --version, -V

    Command-Line Format --version

    Prints the NDB Cluster version number of the executable. The version number is relevant because not all versions can be used together, and the NDB Cluster startup process verifies that the versions of the binaries being used can co-exist in the same cluster. This is also important when performing an online (rolling) software upgrade or downgrade of NDB Cluster.

    See Section 23.5.5, “Performing a Rolling Restart of an NDB Cluster”), for more information.

23.5 Management of NDB Cluster

Managing an NDB Cluster involves a number of tasks, the first of which is to configure and start NDB Cluster. This is covered in Section 23.3, “Configuration of NDB Cluster”, and Section 23.4, “NDB Cluster Programs”.

The next few sections cover the management of a running NDB Cluster.

For information about security issues relating to management and deployment of an NDB Cluster, see Section 23.5.17, “NDB Cluster Security Issues”.

There are essentially two methods of actively managing a running NDB Cluster. The first of these is through the use of commands entered into the management client whereby cluster status can be checked, log levels changed, backups started and stopped, and nodes stopped and started. The second method involves studying the contents of the cluster log ndb_node_id_cluster.log; this is usually found in the management server's DataDir directory, but this location can be overridden using the LogDestination option. (Recall that node_id represents the unique identifier of the node whose activity is being logged.) The cluster log contains event reports generated by ndbd. It is also possible to send cluster log entries to a Unix system log.

Some aspects of the cluster's operation can be also be monitored from an SQL node using the SHOW ENGINE NDB STATUS statement.

More detailed information about NDB Cluster operations is available in real time through an SQL interface using the ndbinfo database. For more information, see Section 23.5.14, “ndbinfo: The NDB Cluster Information Database”.

NDB statistics counters provide improved monitoring using the mysql client. These counters, implemented in the NDB kernel, relate to operations performed by or affecting Ndb objects, such as starting, closing, and aborting transactions; primary key and unique key operations; table, range, and pruned scans; blocked threads waiting for various operations to complete; and data and events sent and received by NDB Cluster. The counters are incremented by the NDB kernel whenever NDB API calls are made or data is sent to or received by the data nodes.

mysqld exposes the NDB API statistics counters as system status variables, which can be identified from the prefix common to all of their names (Ndb_api_). The values of these variables can be read in the mysql client from the output of a SHOW STATUS statement, or by querying either the Performance Schema session_status or global_status table. By comparing the values of the status variables before and after the execution of an SQL statement that acts on NDB tables, you can observe the actions taken on the NDB API level that correspond to this statement, which can be beneficial for monitoring and performance tuning of NDB Cluster.

MySQL Cluster Manager provides an advanced command-line interface that simplifies many otherwise complex NDB Cluster management tasks, such as starting, stopping, or restarting an NDB Cluster with a large number of nodes. The MySQL Cluster Manager client also supports commands for getting and setting the values of most node configuration parameters as well as mysqld server options and variables relating to NDB Cluster. MySQL Cluster Manager version 1.4.8 provides experimental support for NDB 8.0. See MySQL™ Cluster Manager 1.4.8 User Manual, for more information.

23.5.1 Commands in the NDB Cluster Management Client

In addition to the central configuration file, a cluster may also be controlled through a command-line interface available through the management client ndb_mgm. This is the primary administrative interface to a running cluster.

Commands for the event logs are given in Section 23.5.3, “Event Reports Generated in NDB Cluster”; commands for creating backups and restoring from them are provided in Section 23.5.8, “Online Backup of NDB Cluster”.

Using ndb_mgm with MySQL Cluster Manager.  MySQL Cluster Manager 1.4.8 provides expermental support for NDB 8.0. MySQL Cluster Manager handles starting and stopping processes and tracks their states internally, so it is not necessary to use ndb_mgm for these tasks for an NDB Cluster that is under MySQL Cluster Manager control. It is recommended not to use the ndb_mgm command-line client that comes with the NDB Cluster distribution to perform operations that involve starting or stopping nodes. These include but are not limited to the START, STOP, RESTART, and SHUTDOWN commands. For more information, see MySQL Cluster Manager Process Commands.

The management client has the following basic commands. In the listing that follows, node_id denotes either a data node ID or the keyword ALL, which indicates that the command should be applied to all of the cluster's data nodes.

  • HELP

    Displays information on all available commands.

  • CONNECT connection-string

    Connects to the management server indicated by the connection string. If the client is already connected to this server, the client reconnects.

  • SHOW

    Displays information on the cluster's status. Possible node status values include UNKNOWN, NO_CONTACT, NOT_STARTED, STARTING, STARTED, SHUTTING_DOWN, and RESTARTING.

    The output from this command also indicates when the cluster is in single user mode (status SINGLE USER MODE). In NDB 8.0.17 and later, it also indicates which API or SQL node has exclusive access when this mode is in effect; this works only when all data nodes and management nodes connected to the cluster are version 8.0.17 or later.

  • node_id START

    Brings online the data node identified by node_id (or all data nodes).

    ALL START works on all data nodes only, and does not affect management nodes.

    Important

    To use this command to bring a data node online, the data node must have been started using --nostart or -n.

  • node_id STOP [-a] [-f]

    Stops the data or management node identified by node_id.

    Note

    ALL STOP works to stop all data nodes only, and does not affect management nodes.

    A node affected by this command disconnects from the cluster, and its associated ndbd or ndb_mgmd process terminates.

    The -a option causes the node to be stopped immediately, without waiting for the completion of any pending transactions.

    Normally, STOP fails if the result would cause an incomplete cluster. The -f option forces the node to shut down without checking for this. If this option is used and the result is an incomplete cluster, the cluster immediately shuts down.

    Warning

    Use of the -a option also disables the safety check otherwise performed when STOP is invoked to insure that stopping the node does not cause an incomplete cluster. In other words, you should exercise extreme care when using the -a option with the STOP command, due to the fact that this option makes it possible for the cluster to undergo a forced shutdown because it no longer has a complete copy of all data stored in NDB.

  • node_id RESTART [-n] [-i] [-a] [-f]

    Restarts the data node identified by node_id (or all data nodes).

    Using the -i option with RESTART causes the data node to perform an initial restart; that is, the node's file system is deleted and recreated. The effect is the same as that obtained from stopping the data node process and then starting it again using ndbd --initial from the system shell.

    Note

    Backup files and Disk Data files are not removed when this option is used.

    Using the -n option causes the data node process to be restarted, but the data node is not actually brought online until the appropriate START command is issued. The effect of this option is the same as that obtained from stopping the data node and then starting it again using ndbd --nostart or ndbd -n from the system shell.

    Using the -a causes all current transactions relying on this node to be aborted. No GCP check is done when the node rejoins the cluster.

    Normally, RESTART fails if taking the node offline would result in an incomplete cluster. The -f option forces the node to restart without checking for this. If this option is used and the result is an incomplete cluster, the entire cluster is restarted.

  • node_id STATUS

    Displays status information for the data node identified by node_id (or for all data nodes).

    The output from this command also indicates when the cluster is in single user mode.

  • node_id REPORT report-type

    Displays a report of type report-type for the data node identified by node_id, or for all data nodes using ALL.

    Currently, there are three accepted values for report-type:

    • BackupStatus provides a status report on a cluster backup in progress

    • MemoryUsage displays how much data memory and index memory is being used by each data node as shown in this example:

      ndb_mgm> ALL REPORT MEMORY
      
      Node 1: Data usage is 5%(177 32K pages of total 3200)
      Node 1: Index usage is 0%(108 8K pages of total 12832)
      Node 2: Data usage is 5%(177 32K pages of total 3200)
      Node 2: Index usage is 0%(108 8K pages of total 12832)
      

      This information is also available from the ndbinfo.memoryusage table.

    • EventLog reports events from the event log buffers of one or more data nodes.

    report-type is case-insensitive and fuzzy; for MemoryUsage, you can use MEMORY (as shown in the prior example), memory, or even simply MEM (or mem). You can abbreviate BackupStatus in a similar fashion.

  • ENTER SINGLE USER MODE node_id

    Enters single user mode, whereby only the MySQL server identified by the node ID node_id is permitted to access the database.

    Beginning with NDB 8.0.17, the ndb_mgm client provides a clear acknowledgement that this command has been issued and has taken effect, as shown here:

    ndb_mgm> ENTER SINGLE USER MODE 100
    Single user mode entered
    Access is granted for API node 100 only.
    

    Also in NDB 8.0.17 and later, the API or SQL node having exclusive access when in single user mode is indicated in the output of the SHOW command, like this:

    ndb_mgm> SHOW
    Cluster Configuration
    ---------------------
    [ndbd(NDB)]     2 node(s)
    id=5    @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, single user mode, Nodegroup: 0, *)
    id=6    @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, single user mode, Nodegroup: 0)
    
    [ndb_mgmd(MGM)] 1 node(s)
    id=50   @127.0.0.1  (mysql-8.0.17 ndb-8.0.17)
    
    [mysqld(API)]   2 node(s)
    id=100  @127.0.0.1  (mysql-8.0.17 ndb-8.0.17, allowed single user)
    id=101 (not connected, accepting connect from any host)
    
    Note

    All data and management nodes must be running version 8.0.17 of the NDB Cluster software for this feature to be enabled.

  • EXIT SINGLE USER MODE

    Exits single user mode, enabling all SQL nodes (that is, all running mysqld processes) to access the database.

    Note

    It is possible to use EXIT SINGLE USER MODE even when not in single user mode, although the command has no effect in this case.

  • QUIT, EXIT

    Terminates the management client.

    This command does not affect any nodes connected to the cluster.

  • SHUTDOWN

    Shuts down all cluster data nodes and management nodes. To exit the management client after this has been done, use EXIT or QUIT.

    This command does not shut down any SQL nodes or API nodes that are connected to the cluster.

  • CREATE NODEGROUP nodeid[, nodeid, ...]

    Creates a new NDB Cluster node group and causes data nodes to join it.

    This command is used after adding new data nodes online to an NDB Cluster, and causes them to join a new node group and thus to begin participating fully in the cluster. The command takes as its sole parameter a comma-separated list of node IDs—these are the IDs of the nodes just added and started that are to join the new node group. The number of nodes must be the same as the number of nodes in each node group that is already part of the cluster (each NDB Cluster node group must have the same number of nodes). In other words, if the NDB Cluster has 2 node groups of 2 data nodes each, then the new node group must also have 2 data nodes.

    The node group ID of the new node group created by this command is determined automatically, and always the next highest unused node group ID in the cluster; it is not possible to set it manually.

    For more information, see Section 23.5.7, “Adding NDB Cluster Data Nodes Online”.

  • DROP NODEGROUP nodegroup_id

    Drops the NDB Cluster node group with the given nodegroup_id.

    This command can be used to drop a node group from an NDB Cluster. DROP NODEGROUP takes as its sole argument the node group ID of the node group to be dropped.

    DROP NODEGROUP acts only to remove the data nodes in the effected node group from that node group. It does not stop data nodes, assign them to a different node group, or remove them from the cluster's configuration. A data node that does not belong to a node group is indicated in the output of the management client SHOW command with no nodegroup in place of the node group ID, like this (indicated using bold text):

    id=3    @10.100.2.67  (8.0.23-ndb-8.0.23, no nodegroup)
    

    DROP NODEGROUP works only when all data nodes in the node group to be dropped are completely empty of any table data and table definitions. Since there is currently no way using ndb_mgm or the mysql client to remove all data from a specific data node or node group, this means that the command succeeds only in the two following cases:

    1. After issuing CREATE NODEGROUP in the ndb_mgm client, but before issuing any ALTER TABLE ... REORGANIZE PARTITION statements in the mysql client.

    2. After dropping all NDBCLUSTER tables using DROP TABLE.

      TRUNCATE TABLE does not work for this purpose because this removes only the table data; the data nodes continue to store an NDBCLUSTER table's definition until a DROP TABLE statement is issued that causes the table metadata to be dropped.

    For more information about DROP NODEGROUP, see Section 23.5.7, “Adding NDB Cluster Data Nodes Online”.

  • PROMPT [prompt]

    Changes the prompt shown by ndb_mgm to the string literal prompt.

    prompt should not be quoted (unless you want the prompt to include the quotation marks). Unlike the case with the mysql client, special character sequences and escapes are not recognized. If called without an argument, the command resets the prompt to the default value (ndb_mgm>).

    Some examples are shown here:

    ndb_mgm> PROMPT mgm#1:
    mgm#1: SHOW
    Cluster Configuration
    ...
    mgm#1: PROMPT mymgm >
    mymgm > PROMPT 'mymgm:'
    'mymgm:' PROMPT  mymgm:
    mymgm: PROMPT
    ndb_mgm> EXIT
    jon@valhaj:~/bin>
    

    Note that leading spaces and spaces within the prompt string are not trimmed. Trailing spaces are removed.

  • node_id NODELOG DEBUG {ON|OFF}

    Toggles debug logging in the node log, as though the effected data node or nodes had been started with the --verbose option. NODELOG DEBUG ON starts debug logging; NODELOG DEBUG OFF switches debug logging off.

Additional commands.  A number of other commands available in the ndb_mgm client are described elsewhere, as shown in the following list:

23.5.2 NDB Cluster Log Messages

This section contains information about the messages written to the cluster log in response to different cluster log events. It provides additional, more specific information on NDB transporter errors.

23.5.2.1 NDB Cluster: Messages in the Cluster Log

The following table lists the most common NDB cluster log messages. For information about the cluster log, log events, and event types, see Section 23.5.3, “Event Reports Generated in NDB Cluster”. These log messages also correspond to log event types in the MGM API; see The Ndb_logevent_type Type, for related information of interest to Cluster API developers.

Table 23.52 Common NDB cluster log messages

Log Message Description Event Name Event Type Priority Severity
Node mgm_node_id: Node data_node_id Connected The data node having node ID node_id has connected to the management server (node mgm_node_id). Connected Connection 8 INFO
Node mgm_node_id: Node data_node_id Disconnected The data node having node ID data_node_id has disconnected from the management server (node mgm_node_id). Disconnected Connection 8 ALERT
Node data_node_id: Communication to Node api_node_id closed The API node or SQL node having node ID api_node_id is no longer communicating with data node data_node_id. CommunicationClosed Connection 8 INFO
Node data_node_id: Communication to Node api_node_id opened The API node or SQL node having node ID api_node_id is now communicating with data node data_node_id. CommunicationOpened Connection 8 INFO
Node mgm_node_id: Node api_node_id: API version The API node having node ID api_node_id has connected to management node mgm_node_id using NDB API version version (generally the same as the MySQL version number). ConnectedApiVersion Connection 8 INFO
Node node_id: Global checkpoint gci started A global checkpoint with the ID gci has been started; node node_id is the master responsible for this global checkpoint. GlobalCheckpointStarted Checkpoint 9 INFO
Node node_id: Global checkpoint gci completed The global checkpoint having the ID gci has been completed; node node_id was the master responsible for this global checkpoint. GlobalCheckpointCompleted Checkpoint 10 INFO
Node node_id: Local checkpoint lcp started. Keep GCI = current_gci oldest restorable GCI = old_gci The local checkpoint having sequence ID lcp has been started on node node_id. The most recent GCI that can be used has the index current_gci, and the oldest GCI from which the cluster can be restored has the index old_gci. LocalCheckpointStarted Checkpoint 7 INFO
Node node_id: Local checkpoint lcp completed The local checkpoint having sequence ID lcp on node node_id has been completed. LocalCheckpointCompleted Checkpoint 8 INFO
Node node_id: Local Checkpoint stopped in CALCULATED_KEEP_GCI The node was unable to determine the most recent usable GCI. LCPStoppedInCalcKeepGci Checkpoint 0 ALERT
Node node_id: Table ID = table_id, fragment ID = fragment_id has completed LCP on Node node_id maxGciStarted: started_gci maxGciCompleted: completed_gci A table fragment has been checkpointed to disk on node node_id. The GCI in progress has the index started_gci, and the most recent GCI to have been completed has the index completed_gci. LCPFragmentCompleted Checkpoint 11 INFO
Node node_id: ACC Blocked num_1 and TUP Blocked num_2 times last second Undo logging is blocked because the log buffer is close to overflowing. UndoLogBlocked Checkpoint 7 INFO
Node node_id: Start initiated version Data node node_id, running NDB version version, is beginning its startup process. NDBStartStarted StartUp 1 INFO
Node node_id: Started version Data node node_id, running NDB version version, has started successfully. NDBStartCompleted StartUp 1 INFO
Node node_id: STTORRY received after restart finished The node has received a signal indicating that a cluster restart has completed. STTORRYRecieved StartUp 15 INFO
Node node_id: Start phase phase completed (type) The node has completed start phase phase of a type start. For a listing of start phases, see Section 23.5.4, “Summary of NDB Cluster Start Phases”. (type is one of initial, system, node, initial node, or <Unknown>.) StartPhaseCompleted StartUp 4 INFO
Node node_id: CM_REGCONF president = president_id, own Node = own_id, our dynamic id = dynamic_id Node president_id has been selected as president. own_id and dynamic_id should always be the same as the ID (node_id) of the reporting node. CM_REGCONF StartUp 3 INFO
Node node_id: CM_REGREF from Node president_id to our Node node_id. Cause = cause The reporting node (ID node_id) was unable to accept node president_id as president. The cause of the problem is given as one of Busy, Election with wait = false, Not president, Election without selecting new candidate, or No such cause. CM_REGREF StartUp 8 INFO
Node node_id: We are Node own_id with dynamic ID dynamic_id, our left neighbor is Node id_1, our right is Node id_2 The node has discovered its neighboring nodes in the cluster (node id_1 and node id_2). node_id, own_id, and dynamic_id should always be the same; if they are not, this indicates a serious misconfiguration of the cluster nodes. FIND_NEIGHBOURS StartUp 8 INFO
Node node_id: type shutdown initiated The node has received a shutdown signal. The type of shutdown is either Cluster or Node. NDBStopStarted StartUp 1 INFO
Node node_id: Node shutdown completed [, action] [Initiated by signal signal.] The node has been shut down. This report may include an action, which if present is one of restarting, no start, or initial. The report may also include a reference to an NDB Protocol signal; for possible signals, refer to Operations and Signals. NDBStopCompleted StartUp 1 INFO
Node node_id: Forced node shutdown completed [, action]. [Occurred during startphase start_phase.] [ Initiated by signal.] [Caused by error error_code: 'error_message(error_classification). error_status'. [(extra info extra_code)]] The node has been forcibly shut down. The action (one of restarting, no start, or initial) subsequently being taken, if any, is also reported. If the shutdown occurred while the node was starting, the report includes the start_phase during which the node failed. If this was a result of a signal sent to the node, this information is also provided (see Operations and Signals, for more information). If the error causing the failure is known, this is also included; for more information about NDB error messages and classifications, see NDB Cluster API Errors. NDBStopForced StartUp 1 ALERT
Node node_id: Node shutdown aborted The node shutdown process was aborted by the user. NDBStopAborted StartUp 1 INFO
Node node_id: StartLog: [GCI Keep: keep_pos LastCompleted: last_pos NewestRestorable: restore_pos] This reports global checkpoints referenced during a node start. The redo log prior to keep_pos is dropped. last_pos is the last global checkpoint in which data node the participated; restore_pos is the global checkpoint which is actually used to restore all data nodes. StartREDOLog StartUp 4 INFO
startup_message [Listed separately; see below.] There are a number of possible startup messages that can be logged under different circumstances. These are listed separately; see Section 23.5.2.2, “NDB Cluster Log Startup Messages”. StartReport StartUp 4 INFO
Node node_id: Node restart completed copy of dictionary information Copying of data dictionary information to the restarted node has been completed. NR_CopyDict NodeRestart 8 INFO
Node node_id: Node restart completed copy of distribution information Copying of data distribution information to the restarted node has been completed. NR_CopyDistr NodeRestart 8 INFO
Node node_id: Node restart starting to copy the fragments to Node node_id Copy of fragments to starting data node node_id has begun NR_CopyFragsStarted NodeRestart 8 INFO
Node node_id: Table ID = table_id, fragment ID = fragment_id have been copied to Node node_id Fragment fragment_id from table table_id has been copied to data node node_id NR_CopyFragDone NodeRestart 10 INFO
Node node_id: Node restart completed copying the fragments to Node node_id Copying of all table fragments to restarting data node node_id has been completed NR_CopyFragsCompleted NodeRestart 8 INFO
Node node_id: Node node1_id completed failure of Node node2_id Data node node1_id has detected the failure of data node node2_id NodeFailCompleted NodeRestart 8 ALERT
All nodes completed failure of Node node_id All (remaining) data nodes have detected the failure of data node node_id NodeFailCompleted NodeRestart 8 ALERT
Node failure of node_idblock completed The failure of data node node_id has been detected in the blockNDB kernel block, where block is 1 of DBTC, DBDICT, DBDIH, or DBLQH; for more information, see NDB Kernel Blocks NodeFailCompleted NodeRestart 8 ALERT
Node mgm_node_id: Node data_node_id has failed. The Node state at failure was state_code A data node has failed. Its state at the time of failure is described by an arbitration state code state_code: possible state code values can be found in the file include/kernel/signaldata/ArbitSignalData.hpp. NODE_FAILREP NodeRestart 8 ALERT
President restarts arbitration thread [state=state_code] or Prepare arbitrator node node_id [ticket=ticket_id] or Receive arbitrator node node_id [ticket=ticket_id] or Started arbitrator node node_id [ticket=ticket_id] or Lost arbitrator node node_id - process failure [state=state_code] or Lost arbitrator node node_id - process exit [state=state_code] or Lost arbitrator node node_id - error_message [state=state_code] This is a report on the current state and progress of arbitration in the cluster. node_id is the node ID of the management node or SQL node selected as the arbitrator. state_code is an arbitration state code, as found in include/kernel/signaldata/ArbitSignalData.hpp. When an error has occurred, an error_message, also defined in ArbitSignalData.hpp, is provided. ticket_id is a unique identifier handed out by the arbitrator when it is selected to all the nodes that participated in its selection; this is used to ensure that each node requesting arbitration was one of the nodes that took part in the selection process. ArbitState NodeRestart 6 INFO
Arbitration check lost - less than 1/2 nodes left or Arbitration check won - all node groups and more than 1/2 nodes left or Arbitration check won - node group majority or Arbitration check lost - missing node group or Network partitioning - arbitration required or Arbitration won - positive reply from node node_id or Arbitration lost - negative reply from node node_id or Network partitioning - no arbitrator available or Network partitioning - no arbitrator configured or Arbitration failure - error_message [state=state_code] This message reports on the result of arbitration. In the event of arbitration failure, an error_message and an arbitration state_code are provided; definitions for both of these are found in include/kernel/signaldata/ArbitSignalData.hpp. ArbitResult NodeRestart 2 ALERT
Node node_id: GCP Take over started This node is attempting to assume responsibility for the next global checkpoint (that is, it is becoming the master node) GCP_TakeoverStarted NodeRestart 7 INFO
Node node_id: GCP Take over completed This node has become the master, and has assumed responsibility for the next global checkpoint GCP_TakeoverCompleted NodeRestart 7 INFO
Node node_id: LCP Take over started This node is attempting to assume responsibility for the next set of local checkpoints (that is, it is becoming the master node) LCP_TakeoverStarted NodeRestart 7 INFO
Node node_id: LCP Take over completed This node has become the master, and has assumed responsibility for the next set of local checkpoints LCP_TakeoverCompleted NodeRestart 7 INFO
Node node_id: Trans. Count = transactions, Commit Count = commits, Read Count = reads, Simple Read Count = simple_reads, Write Count = writes, AttrInfo Count = AttrInfo_objects, Concurrent Operations = concurrent_operations, Abort Count = aborts, Scans = scans, Range scans = range_scans This report of transaction activity is given approximately once every 10 seconds TransReportCounters Statistic 8 INFO
Node node_id: Operations=operations Number of operations performed by this node, provided approximately once every 10 seconds OperationReportCounters Statistic 8 INFO
Node node_id: Table with ID = table_id created A table having the table ID shown has been created TableCreated Statistic 7 INFO
Node node_id: Mean loop Counter in doJob last 8192 times = count JobStatistic Statistic 9 INFO
Mean send size to Node = node_id last 4096 sends = bytes bytes This node is sending an average of bytes bytes per send to node node_id SendBytesStatistic Statistic 9 INFO
Mean receive size to Node = node_id last 4096 sends = bytes bytes This node is receiving an average of bytes of data each time it receives data from node node_id ReceiveBytesStatistic Statistic 9 INFO
Node node_id: Data usage is data_memory_percentage% (data_pages_used 32K pages of total data_pages_total) / Node node_id: Index usage is index_memory_percentage% (index_pages_used 8K pages of total index_pages_total) This report is generated when a DUMP 1000 command is issued in the cluster management client MemoryUsage Statistic 5 INFO
Node node1_id: Transporter to node node2_id reported error error_code: error_message A transporter error occurred while communicating with node node2_id; for a listing of transporter error codes and messages, see NDB Transporter Errors, in MySQL NDB Cluster Internals Manual TransporterError Error 2 ERROR
Node node1_id: Transporter to node node2_id reported error error_code: error_message A warning of a potential transporter problem while communicating with node node2_id; for a listing of transporter error codes and messages, see NDB Transporter Errors, for more information TransporterWarning Error 8 WARNING
Node node1_id: Node node2_id missed heartbeat heartbeat_id This node missed a heartbeat from node node2_id MissedHeartbeat Error 8 WARNING
Node node1_id: Node node2_id declared dead due to missed heartbeat This node has missed at least 3 heartbeats from node node2_id, and so has declared that node dead DeadDueToHeartbeat Error 8 ALERT
Node node1_id: Node Sent Heartbeat to node = node2_id This node has sent a heartbeat to node node2_id SentHeartbeat Info 12 INFO
Node node_id: Event buffer status (object_id): used=bytes_used (percent_used% of alloc) alloc=bytes_allocated max=bytes_available latest_consumed_epoch=latest_consumed_epoch latest_buffered_epoch=latest_buffered_epoch report_reason=report_reason This report is seen during heavy event buffer usage, for example, when many updates are being applied in a relatively short period of time; the report shows the number of bytes and the percentage of event buffer memory used, the bytes allocated and percentage still available, and the latest buffered and consumed epochs; for more information, see Section 23.5.2.3, “Event Buffer Reporting in the Cluster Log” EventBufferStatus2 Info 7 INFO
Node node_id: Entering single user mode, Node node_id: Entered single user mode Node API_node_id has exclusive access, Node node_id: Entering single user mode These reports are written to the cluster log when entering and exiting single user mode; API_node_id is the node ID of the API or SQL having exclusive access to the cluster (for more information, see Section 23.5.6, “NDB Cluster Single User Mode”); the message Unknown single user report API_node_id indicates an error has taken place and should never be seen in normal operation SingleUser Info 7 INFO
Node node_id: Backup backup_id started from node mgm_node_id A backup has been started using the management node having mgm_node_id; this message is also displayed in the cluster management client when the START BACKUP command is issued; for more information, see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup” BackupStarted Backup 7 INFO
Node node_id: Backup backup_id started from node mgm_node_id completed. StartGCP: start_gcp StopGCP: stop_gcp #Records: records #LogRecords: log_records Data: data_bytes bytes Log: log_bytes bytes The backup having the ID backup_id has been completed; for more information, see Section 23.5.8.2, “Using The NDB Cluster Management Client to Create a Backup” BackupCompleted Backup 7 INFO
Node node_id: Backup request from mgm_node_id failed to start. Error: error_code The backup failed to start; for error codes, see MGM API Errors BackupFailedToStart Backup 7 ALERT
Node node_id: Backup backup_id started from mgm_node_id has been aborted. Error: error_code The backup was terminated after starting, possibly due to user intervention BackupAborted Backup 7 ALERT

23.5.2.2 NDB Cluster Log Startup Messages

Possible startup messages with descriptions are provided in the following list:

  • Initial start, waiting for %s to connect, nodes [ all: %s connected: %s no-wait: %s ]

  • Waiting until nodes: %s connects, nodes [ all: %s connected: %s no-wait: %s ]

  • Waiting %u sec for nodes %s to connect, nodes [ all: %s connected: %s no-wait: %s ]

  • Waiting for non partitioned start, nodes [ all: %s connected: %s missing: %s no-wait: %s ]

  • Waiting %u sec for non partitioned start, nodes [ all: %s connected: %s missing: %s no-wait: %s ]

  • Initial start with nodes %s [ missing: %s no-wait: %s ]

  • Start with all nodes %s

  • Start with nodes %s [ missing: %s no-wait: %s ]

  • Start potentially partitioned with nodes %s [ missing: %s no-wait: %s ]

  • Unknown startreport: 0x%x [ %s %s %s %s ]

23.5.2.3 Event Buffer Reporting in the Cluster Log

NDB uses one or more memory buffers for events received from the data nodes. There is one such buffer for each Ndb object subscribing to table events, which means that there are usually two buffers for each mysqld performing binary logging (one buffer for schema events, and one for data events). Each buffer contains epochs made up of events. These events consist of operation types (insert, update, delete) and row data (before and after images plus metadata).

NDB generates messages in the cluster log to describe the state of these buffers. Although these reports appear in the cluster log, they refer to buffers on API nodes (unlike most other cluster log messages, which are generated by data nodes).

Event buffer logging reports in the cluster log use the format shown here:

Node node_id: Event buffer status (object_id):
used=bytes_used (percent_used% of alloc)
alloc=bytes_allocated (percent_alloc% of max) max=bytes_available
latest_consumed_epoch=latest_consumed_epoch
latest_buffered_epoch=latest_buffered_epoch
report_reason=report_reason

The fields making up this report are listed here, with descriptions:

  • node_id: ID of the node where the report originated.

  • object_id: ID of the Ndb object where the report originated.

  • bytes_used: Number of bytes used by the buffer.

  • percent_used: Percentage of allocated bytes used.

  • bytes_allocated: Number of bytes allocated to this buffer.

  • percent_alloc: Percentage of available bytes used; not printed if ndb_eventbuffer_max_alloc is equal to 0 (unlimited).

  • bytes_available: Number of bytes available; this is 0 if ndb_eventbuffer_max_alloc is 0 (unlimited).

  • latest_consumed_epoch: The epoch most recently consumed to completion. (In NDB API applications, this is done by calling nextEvent().)

  • latest_buffered_epoch: The epoch most recently buffered (completely) in the event buffer.

  • report_reason: The reason for making the report. Possible reasons are shown later in this section.

Possible reasons for reporting are described in the following list:

  • ENOUGH_FREE_EVENTBUFFER: The event buffer has sufficient space.

    LOW_FREE_EVENTBUFFER: The event buffer is running low on free space.

    The threshold free percentage level triggering these reports can be adjusted by setting the ndb_report_thresh_binlog_mem_usage server variable.

  • BUFFERED_EPOCHS_OVER_THRESHOLD: Whether the number of buffered epochs has exceeded the configured threshold. This number is the difference between the latest epoch that has been received in its entirety and the epoch that has most recently been consumed (in NDB API applications, this is done by calling nextEvent() or nextEvent2()). The report is generated every second until the number of buffered epochs goes below the threshold, which can be adjusted by setting the ndb_report_thresh_binlog_epoch_slip server variable. You can also adjust the threshold in NDB API applications by calling setEventBufferQueueEmptyEpoch().

  • PARTIALLY_DISCARDING: Event buffer memory is exhausted—that is, 100% of ndb_eventbuffer_max_alloc has been used. Any partially buffered epoch is buffered to completion even is usage exceeds 100%, but any new epochs received are discarded. This means that a gap has occurred in the event stream.

  • COMPLETELY_DISCARDING: No epochs are buffered.

  • PARTIALLY_BUFFERING: The buffer free percentage following the gap has risen to the threshold, which can be set in the mysql client using the ndb_eventbuffer_free_percent server system variable or in NDB API applications by calling set_eventbuffer_free_percent(). New epochs are buffered. Epochs that could not be completed due to the gap are discarded.

  • COMPLETELY_BUFFERING: All epochs received are being buffered, which means that there is sufficient event buffer memory. The gap in the event stream has been closed.

23.5.2.4 NDB Cluster: NDB Transporter Errors

This section lists error codes, names, and messages that are written to the cluster log in the event of transporter errors.

0x00

TE_NO_ERROR

No error

0x01

TE_ERROR_CLOSING_SOCKET

Error found during closing of socket

0x02

TE_ERROR_IN_SELECT_BEFORE_ACCEPT

Error found before accept. The transporter will retry

0x03

TE_INVALID_MESSAGE_LENGTH

Error found in message (invalid message length)

0x04

TE_INVALID_CHECKSUM

Error found in message (checksum)

0x05

TE_COULD_NOT_CREATE_SOCKET

Error found while creating socket(can't create socket)

0x06

TE_COULD_NOT_BIND_SOCKET

Error found while binding server socket

0x07

TE_LISTEN_FAILED

Error found while listening to server socket

0x08

TE_ACCEPT_RETURN_ERROR

Error found during accept(accept return error)

0x0b

TE_SHM_DISCONNECT

The remote node has disconnected

0x0c

TE_SHM_IPC_STAT

Unable to check shm segment

0x0d

TE_SHM_UNABLE_TO_CREATE_SEGMENT

Unable to create shm segment

0x0e

TE_SHM_UNABLE_TO_ATTACH_SEGMENT

Unable to attach shm segment

0x0f

TE_SHM_UNABLE_TO_REMOVE_SEGMENT

Unable to remove shm segment

0x10

TE_TOO_SMALL_SIGID

Sig ID too small

0x11

TE_TOO_LARGE_SIGID

Sig ID too large

0x12

TE_WAIT_STACK_FULL

Wait stack was full

0x13

TE_RECEIVE_BUFFER_FULL

Receive buffer was full

0x14

TE_SIGNAL_LOST_SEND_BUFFER_FULL

Send buffer was full,and trying to force send fails

0x15

TE_SIGNAL_LOST

Send failed for unknown reason(signal lost)

0x16

TE_SEND_BUFFER_FULL

The send buffer was full, but sleeping for a while solved

0x21

TE_SHM_IPC_PERMANENT

Shm ipc Permanent error

Note

Transporter error codes 0x17 through 0x20 and 0x22 are reserved for SCI connections, which are not supported in this version of NDB Cluster, and so are not included here.

23.5.3 Event Reports Generated in NDB Cluster

In this section, we discuss the types of event logs provided by NDB Cluster, and the types of events that are logged.

NDB Cluster provides two types of event log:

  • The cluster log, which includes events generated by all cluster nodes. The cluster log is the log recommended for most uses because it provides logging information for an entire cluster in a single location.

    By default, the cluster log is saved to a file named ndb_node_id_cluster.log, (where node_id is the node ID of the management server) in the management server's DataDir.

    Cluster logging information can also be sent to stdout or a syslog facility in addition to or instead of being saved to a file, as determined by the values set for the DataDir and LogDestination configuration parameters. See Section 23.3.3.5, “Defining an NDB Cluster Management Server”, for more information about these parameters.

  • Node logs are local to each node.

    Output generated by node event logging is written to the file ndb_node_id_out.log (where node_id is the node's node ID) in the node's DataDir. Node event logs are generated for both management nodes and data nodes.

    Node logs are intended to be used only during application development, or for debugging application code.

Both types of event logs can be set to log different subsets of events.

Each reportable event can be distinguished according to three different criteria:

  • Category: This can be any one of the following values: STARTUP, SHUTDOWN, STATISTICS, CHECKPOINT, NODERESTART, CONNECTION, ERROR, or INFO.

  • Priority: This is represented by one of the numbers from 0 to 15 inclusive, where 0 indicates most important and 15 least important.

  • Severity Level: This can be any one of the following values: ALERT, CRITICAL, ERROR, WARNING, INFO, or DEBUG.

Both the cluster log and the node log can be filtered on these properties.

The format used in the cluster log is as shown here:

2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Data usage is 2%(60 32K pages of total 2560)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Index usage is 1%(24 8K pages of total 2336)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Resource 0 min: 0 max: 639 curr: 0
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Data usage is 2%(76 32K pages of total 2560)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Index usage is 1%(24 8K pages of total 2336)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Resource 0 min: 0 max: 639 curr: 0
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Data usage is 2%(58 32K pages of total 2560)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Index usage is 1%(25 8K pages of total 2336)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Resource 0 min: 0 max: 639 curr: 0
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Data usage is 2%(74 32K pages of total 2560)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Index usage is 1%(25 8K pages of total 2336)
2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Resource 0 min: 0 max: 639 curr: 0
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 4: Node 9 Connected
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 1: Node 9 Connected
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 1: Node 9: API 8.0.23-ndb-8.0.23
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 2: Node 9 Connected
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 2: Node 9: API 8.0.23-ndb-8.0.23
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 3: Node 9 Connected
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 3: Node 9: API 8.0.23-ndb-8.0.23
2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 4: Node 9: API 8.0.23-ndb-8.0.23
2007-01-26 19:59:22 [MgmSrvr] ALERT    -- Node 2: Node 7 Disconnected
2007-01-26 19:59:22 [MgmSrvr] ALERT    -- Node 2: Node 7 Disconnected

Each line in the cluster log contains the following information:

  • A timestamp in YYYY-MM-DD HH:MM:SS format.

  • The type of node which is performing the logging. In the cluster log, this is always [MgmSrvr].

  • The severity of the event.

  • The ID of the node reporting the event.

  • A description of the event. The most common types of events to appear in the log are connections and disconnections between different nodes in the cluster, and when checkpoints occur. In some cases, the description may contain status information.

23.5.3.1 NDB Cluster Logging Management Commands

ndb_mgm supports a number of management commands related to the cluster log and node logs. In the listing that follows, node_id denotes either a storage node ID or the keyword ALL, which indicates that the command should be applied to all of the cluster's data nodes.

  • CLUSTERLOG ON

    Turns the cluster log on.

  • CLUSTERLOG OFF

    Turns the cluster log off.

  • CLUSTERLOG INFO

    Provides information about cluster log settings.

  • node_id CLUSTERLOG category=threshold

    Logs category events with priority less than or equal to threshold in the cluster log.

  • CLUSTERLOG FILTER severity_level

    Toggles cluster logging of events of the specified severity_level.

The following table describes the default setting (for all data nodes) of the cluster log category threshold. If an event has a priority with a value lower than or equal to the priority threshold, it is reported in the cluster log.

Note

Events are reported per data node, and that the threshold can be set to different values on different nodes.

Table 23.53 Cluster log categories, with default threshold setting

Category Default threshold (All data nodes)
STARTUP 7
SHUTDOWN 7
STATISTICS 7
CHECKPOINT 7
NODERESTART 7
CONNECTION 7
ERROR 15
INFO 7

The STATISTICS category can provide a great deal of useful data. See Section 23.5.3.3, “Using CLUSTERLOG STATISTICS in the NDB Cluster Management Client”, for more information.

Thresholds are used to filter events within each category. For example, a STARTUP event with a priority of 3 is not logged unless the threshold for STARTUP is set to 3 or higher. Only events with priority 3 or lower are sent if the threshold is 3.

The following table shows the event severity levels.

Note

These correspond to Unix syslog levels, except for LOG_EMERG and LOG_NOTICE, which are not used or mapped.

Table 23.54 Event severity levels

Severity Level Value Severity Description
1 ALERT A condition that should be corrected immediately, such as a corrupted system database
2 CRITICAL Critical conditions, such as device errors or insufficient resources
3 ERROR Conditions that should be corrected, such as configuration errors
4 WARNING Conditions that are not errors, but that might require special handling
5 INFO Informational messages
6 DEBUG Debugging messages used for NDBCLUSTER development

Event severity levels can be turned on or off (using CLUSTERLOG FILTER—see above). If a severity level is turned on, then all events with a priority less than or equal to the category thresholds are logged. If the severity level is turned off then no events belonging to that severity level are logged.

Important

Cluster log levels are set on a per ndb_mgmd, per subscriber basis. This means that, in an NDB Cluster with multiple management servers, using a CLUSTERLOG command in an instance of ndb_mgm connected to one management server affects only logs generated by that management server but not by any of the others. This also means that, should one of the management servers be restarted, only logs generated by that management server are affected by the resetting of log levels caused by the restart.

23.5.3.2 NDB Cluster Log Events

An event report reported in the event logs has the following format:

datetime [string] severity -- message

For example:

09:19:30 2005-07-24 [NDB] INFO -- Node 4 Start phase 4 completed

This section discusses all reportable events, ordered by category and severity level within each category.

In the event descriptions, GCP and LCP mean Global Checkpoint and Local Checkpoint, respectively.

CONNECTION Events

These events are associated with connections between Cluster nodes.

Table 23.55 Events associated with connections between cluster nodes

Event Priority Severity Level Description
Connected 8 INFO Data nodes connected
Disconnected 8 ALERT Data nodes disconnected
CommunicationClosed 8 INFO SQL node or data node connection closed
CommunicationOpened 8 INFO SQL node or data node connection open
ConnectedApiVersion 8 INFO Connection using API version

CHECKPOINT Events

The logging messages shown here are associated with checkpoints.

Table 23.56 Events associated with checkpoints

Event Priority Severity Level Description
GlobalCheckpointStarted 9 INFO Start of GCP: REDO log is written to disk
GlobalCheckpointCompleted 10 INFO GCP finished
LocalCheckpointStarted 7 INFO Start of LCP: data written to disk
LocalCheckpointCompleted 7 INFO LCP completed normally
LCPStoppedInCalcKeepGci 0 ALERT LCP stopped
LCPFragmentCompleted 11 INFO LCP on a fragment has been completed
UndoLogBlocked 7 INFO UNDO logging blocked; buffer near overflow
RedoStatus 7 INFO Redo status

STARTUP Events

The following events are generated in response to the startup of a node or of the cluster and of its success or failure. They also provide information relating to the progress of the startup process, including information concerning logging activities.

Table 23.57 Events relating to the startup of a node or cluster

Event Priority Severity Level Description
NDBStartStarted 1 INFO Data node start phases initiated (all nodes starting)
NDBStartCompleted 1 INFO Start phases completed, all data nodes
STTORRYRecieved 15 INFO Blocks received after completion of restart
StartPhaseCompleted 4 INFO Data node start phase X completed
CM_REGCONF 3 INFO Node has been successfully included into the cluster; shows the node, managing node, and dynamic ID
CM_REGREF 8 INFO Node has been refused for inclusion in the cluster; cannot be included in cluster due to misconfiguration, inability to establish communication, or other problem
FIND_NEIGHBOURS 8 INFO Shows neighboring data nodes
NDBStopStarted 1 INFO Data node shutdown initiated
NDBStopCompleted 1 INFO Data node shutdown complete
NDBStopForced 1 ALERT Forced shutdown of data node
NDBStopAborted 1 INFO Unable to shut down data node normally
StartREDOLog 4 INFO New redo log started; GCI keep X, newest restorable GCI Y
StartLog 10 INFO New log started; log part X, start MB Y, stop MB Z
UNDORecordsExecuted 15 INFO Undo records executed
StartReport 4 INFO Report started
LogFileInitStatus 7 INFO Log file initialization status
LogFileInitCompStatus 7 INFO Log file completion status
StartReadLCP 10 INFO Start read for local checkpoint
ReadLCPComplete 10 INFO Read for local checkpoint completed
RunRedo 8 INFO Running the redo log
RebuildIndex 10 INFO Rebuilding indexes

NODERESTART Events

The following events are generated when restarting a node and relate to the success or failure of the node restart process.

Table 23.58 Events relating to restarting a node

Event Priority Severity Level Description
NR_CopyDict 7 INFO Completed copying of dictionary information
NR_CopyDistr 7 INFO Completed copying distribution information
NR_CopyFragsStarted 7 INFO Starting to copy fragments
NR_CopyFragDone 10 INFO Completed copying a fragment
NR_CopyFragsCompleted 7 INFO Completed copying all fragments
NodeFailCompleted 8 ALERT Node failure phase completed
NODE_FAILREP 8 ALERT Reports that a node has failed
ArbitState 6 INFO Report whether an arbitrator is found or not; there are seven different possible outcomes when seeking an arbitrator, listed here:
  • Management server restarts arbitration thread [state=X]

  • Prepare arbitrator node X [ticket=Y]

  • Receive arbitrator node X [ticket=Y]

  • Started arbitrator node X [ticket=Y]

  • Lost arbitrator node X - process failure [state=Y]

  • Lost arbitrator node X - process exit [state=Y]

  • Lost arbitrator node X <error msg> [state=Y]

ArbitResult 2 ALERT Report arbitrator results; there are eight different possible results for arbitration attempts, listed here:
  • Arbitration check failed: less than 1/2 nodes left

  • Arbitration check succeeded: node group majority

  • Arbitration check failed: missing node group

  • Network partitioning: arbitration required

  • Arbitration succeeded: affirmative response from node X

  • Arbitration failed: negative response from node X

  • Network partitioning: no arbitrator available

  • Network partitioning: no arbitrator configured

GCP_TakeoverStarted 7 INFO GCP takeover started
GCP_TakeoverCompleted 7 INFO GCP takeover complete
LCP_TakeoverStarted 7 INFO LCP takeover started
LCP_TakeoverCompleted 7 INFO LCP takeover complete (state = X)
ConnectCheckStarted 6 INFO Connection check started
ConnectCheckCompleted 6 INFO Connection check completed
NodeFailRejected 6 ALERT Node failure phase failed

STATISTICS Events

The following events are of a statistical nature. They provide information such as numbers of transactions and other operations, amount of data sent or received by individual nodes, and memory usage.

Table 23.59 Events of a statistical nature

Event Priority Severity Level Description
TransReportCounters 8 INFO Report transaction statistics, including numbers of transactions, commits, reads, simple reads, writes, concurrent operations, attribute information, and aborts
OperationReportCounters 8 INFO Number of operations
TableCreated 7 INFO Report number of tables created
JobStatistic 9 INFO Mean internal job scheduling statistics
ThreadConfigLoop 9 INFO Number of thread configuration loops
SendBytesStatistic 9 INFO Mean number of bytes sent to node X
ReceiveBytesStatistic 9 INFO Mean number of bytes received from node X
MemoryUsage 5 INFO Data and index memory usage (80%, 90%, and 100%)
MTSignalStatistics 9 INFO Multithreaded signals

SCHEMA Events

These events relate to NDB Cluster schema operations.

Table 23.60 Events relating to NDB Cluster schema operations

Event Priority Severity Level Description
CreateSchemaObject 8 INFO Schema objected created
AlterSchemaObject 8 INFO Schema object updated
DropSchemaObject 8 INFO Schema object dropped

ERROR Events

These events relate to Cluster errors and warnings. The presence of one or more of these generally indicates that a major malfunction or failure has occurred.

Table 23.61 Events relating to cluster errors and warnings

Event Priority Severity Level Description
TransporterError 2 ERROR Transporter error
TransporterWarning 8 WARNING Transporter warning
MissedHeartbeat 8 WARNING Node X missed heartbeat number Y
DeadDueToHeartbeat 8 ALERT Node X declared dead due to missed heartbeat
WarningEvent 2 WARNING General warning event
SubscriptionStatus 4 WARNING Change in subscription status

INFO Events

These events provide general information about the state of the cluster and activities associated with Cluster maintenance, such as logging and heartbeat transmission.

Table 23.62 Information events

Event Priority Severity Level Description
SentHeartbeat 12 INFO Sent heartbeat
CreateLogBytes 11 INFO Create log: Log part, log file, size in MB
InfoEvent 2 INFO General informational event
EventBufferStatus 7 INFO Event buffer status
EventBufferStatus2 7 INFO Improved event buffer status information

Note

SentHeartbeat events are available only if NDB Cluster was compiled with VM_TRACE enabled.

SINGLEUSER Events

These events are associated with entering and exiting single user mode.

Table 23.63 Events relating to single user mode

Event Priority Severity Level Description
SingleUser 7 INFO Entering or exiting single user mode

BACKUP Events

These events provide information about backups being created or restored.

Table 23.64 Backup events

Event Priority Severity Level Description
BackupStarted 7 INFO Backup started
BackupStatus 7 INFO Backup status
BackupCompleted 7 INFO Backup completed
BackupFailedToStart 7 ALERT Backup failed to start
BackupAborted 7 ALERT Backup aborted by user
RestoreStarted 7 INFO Started restoring from backup
RestoreMetaData 7 INFO Restoring metadata
RestoreData 7 INFO Restoring data
RestoreLog 7 INFO Restoring log files
RestoreCompleted 7 INFO Completed restoring from backup
SavedEvent 7 INFO Event saved

23.5.3.3 Using CLUSTERLOG STATISTICS in the NDB Cluster Management Client

The NDB management client's CLUSTERLOG STATISTICS command can provide a number of useful statistics in its output. Counters providing information about the state of the cluster are updated at 5-second reporting intervals by the transaction coordinator (TC) and the local query handler (LQH), and written to the cluster log.

Transaction coordinator statistics.  Each transaction has one transaction coordinator, which is chosen by one of the following methods:

  • In a round-robin fashion

  • By communication proximity

  • By supplying a data placement hint when the transaction is started

Note

You can determine which TC selection method is used for transactions started from a given SQL node using the ndb_optimized_node_selection system variable.

All operations within the same transaction use the same transaction coordinator, which reports the following statistics:

  • Trans count.  This is the number transactions started in the last interval using this TC as the transaction coordinator. Any of these transactions may have committed, have been aborted, or remain uncommitted at the end of the reporting interval.

    Note

    Transactions do not migrate between TCs.

  • Commit count.  This is the number of transactions using this TC as the transaction coordinator that were committed in the last reporting interval. Because some transactions committed in this reporting interval may have started in a previous reporting interval, it is possible for Commit count to be greater than Trans count.

  • Read count.  This is the number of primary key read operations using this TC as the transaction coordinator that were started in the last reporting interval, including simple reads. This count also includes reads performed as part of unique index operations. A unique index read operation generates 2 primary key read operations—1 for the hidden unique index table, and 1 for the table on which the read takes place.

  • Simple read count.  This is the number of simple read operations using this TC as the transaction coordinator that were started in the last reporting interval.

  • Write count.  This is the number of primary key write operations using this TC as the transaction coordinator that were started in the last reporting interval. This includes all inserts, updates, writes and deletes, as well as writes performed as part of unique index operations.

    Note

    A unique index update operation can generate multiple PK read and write operations on the index table and on the base table.

  • AttrInfoCount.  This is the number of 32-bit data words received in the last reporting interval for primary key operations using this TC as the transaction coordinator. For reads, this is proportional to the number of columns requested. For inserts and updates, this is proportional to the number of columns written, and the size of their data. For delete operations, this is usually zero.

    Unique index operations generate multiple PK operations and so increase this count. However, data words sent to describe the PK operation itself, and the key information sent, are not counted here. Attribute information sent to describe columns to read for scans, or to describe ScanFilters, is also not counted in AttrInfoCount.

  • Concurrent Operations.  This is the number of primary key or scan operations using this TC as the transaction coordinator that were started during the last reporting interval but that were not completed. Operations increment this counter when they are started and decrement it when they are completed; this occurs after the transaction commits. Dirty reads and writes—as well as failed operations—decrement this counter.

    The maximum value that Concurrent Operations can have is the maximum number of operations that a TC block can support; currently, this is (2 * MaxNoOfConcurrentOperations) + 16 + MaxNoOfConcurrentTransactions. (For more information about these configuration parameters, see the Transaction Parameters section of Section 23.3.3.6, “Defining NDB Cluster Data Nodes”.)

  • Abort count.  This is the number of transactions using this TC as the transaction coordinator that were aborted during the last reporting interval. Because some transactions that were aborted in the last reporting interval may have started in a previous reporting interval, Abort count can sometimes be greater than Trans count.

  • Scans.  This is the number of table scans using this TC as the transaction coordinator that were started during the last reporting interval. This does not include range scans (that is, ordered index scans).

  • Range scans.  This is the number of ordered index scans using this TC as the transaction coordinator that were started in the last reporting interval.

  • Local reads.  This is the number of primary-key read operations performed using a transaction coordinator on a node that also holds the primary fragment replica of the record. This count can also be obtained from the LOCAL_READS counter in the ndbinfo.counters table.

  • Local writes.  This contains the number of primary-key read operations that were performed using a transaction coordinator on a node that also holds the primary fragment replica of the record. This count can also be obtained from the LOCAL_WRITES counter in the ndbinfo.counters table.

Local query handler statistics (Operations).  There is 1 cluster event per local query handler block (that is, 1 per data node process). Operations are recorded in the LQH where the data they are operating on resides.

Note

A single transaction may operate on data stored in multiple LQH blocks.

The Operations statistic provides the number of local operations performed by this LQH block in the last reporting interval, and includes all types of read and write operations (insert, update, write, and delete operations). This also includes operations used to replicate writes. For example, in a cluster with two fragment replicas, the write to the primary fragment replica is recorded in the primary LQH, and the write to the backup is recorded in the backup LQH. Unique key operations may result in multiple local operations; however, this does not include local operations generated as a result of a table scan or ordered index scan, which are not counted.

Process scheduler statistics.  In addition to the statistics reported by the transaction coordinator and local query handler, each ndbd process has a scheduler which also provides useful metrics relating to the performance of an NDB Cluster. This scheduler runs in an infinite loop; during each loop the scheduler performs the following tasks:

  1. Read any incoming messages from sockets into a job buffer.

  2. Check whether there are any timed messages to be executed; if so, put these into the job buffer as well.

  3. Execute (in a loop) any messages in the job buffer.

  4. Send any distributed messages that were generated by executing the messages in the job buffer.

  5. Wait for any new incoming messages.

Process scheduler statistics include the following:

  • Mean Loop Counter.  This is the number of loops executed in the third step from the preceding list. This statistic increases in size as the utilization of the TCP/IP buffer improves. You can use this to monitor changes in performance as you add new data node processes.

  • Mean send size and Mean receive size.  These statistics enable you to gauge the efficiency of, respectively writes and reads between nodes. The values are given in bytes. Higher values mean a lower cost per byte sent or received; the maximum value is 64K.

To cause all cluster log statistics to be logged, you can use the following command in the NDB management client:

ndb_mgm> ALL CLUSTERLOG STATISTICS=15
Note

Setting the threshold for STATISTICS to 15 causes the cluster log to become very verbose, and to grow quite rapidly in size, in direct proportion to the number of cluster nodes and the amount of activity in the NDB Cluster.

For more information about NDB Cluster management client commands relating to logging and reporting, see Section 23.5.3.1, “NDB Cluster Logging Management Commands”.

23.5.4 Summary of NDB Cluster Start Phases

This section provides a simplified outline of the steps involved when NDB Cluster data nodes are started. More complete information can be found in NDB Cluster Start Phases, in the NDB Internals Guide.

These phases are the same as those reported in the output from the node_id STATUS command in the management client (see Section 23.5.1, “Commands in the NDB Cluster Management Client”). These start phases are also reported in the start_phase column of the ndbinfo.nodes table.

Start types.  There are several different startup types and modes, as shown in the following list:

  • Initial start.  The cluster starts with a clean file system on all data nodes. This occurs either when the cluster started for the very first time, or when all data nodes are restarted using the --initial option.

    Note

    Disk Data files are not removed when restarting a node using --initial.

  • System restart.  The cluster starts and reads data stored in the data nodes. This occurs when the cluster has been shut down after having been in use, when it is desired for the cluster to resume operations from the point where it left off.

  • Node restart.  This is the online restart of a cluster node while the cluster itself is running.

  • Initial node restart.  This is the same as a node restart, except that the node is reinitialized and started with a clean file system.

Setup and initialization (phase -1).  Prior to startup, each data node (ndbd process) must be initialized. Initialization consists of the following steps:

  1. Obtain a node ID

  2. Fetch configuration data

  3. Allocate ports to be used for inter-node communications

  4. Allocate memory according to settings obtained from the configuration file

When a data node or SQL node first connects to the management node, it reserves a cluster node ID. To make sure that no other node allocates the same node ID, this ID is retained until the node has managed to connect to the cluster and at least one ndbd reports that this node is connected. This retention of the node ID is guarded by the connection between the node in question and ndb_mgmd.

After each data node has been initialized, the cluster startup process can proceed. The stages which the cluster goes through during this process are listed here:

  • Phase 0.  The NDBFS and NDBCNTR blocks start. Data node file systems are cleared on those data nodes that were started with --initial option.

  • Phase 1.  In this stage, all remaining NDB kernel blocks are started. NDB Cluster connections are set up, inter-block communications are established, and heartbeats are started. In the case of a node restart, API node connections are also checked.

    Note

    When one or more nodes hang in Phase 1 while the remaining node or nodes hang in Phase 2, this often indicates network problems. One possible cause of such issues is one or more cluster hosts having multiple network interfaces. Another common source of problems causing this condition is the blocking of TCP/IP ports needed for communications between cluster nodes. In the latter case, this is often due to a misconfigured firewall.

  • Phase 2.  The NDBCNTR kernel block checks the states of all existing nodes. The master node is chosen, and the cluster schema file is initialized.

  • Phase 3.  The DBLQH and DBTC kernel blocks set up communications between them. The startup type is determined; if this is a restart, the DBDIH block obtains permission to perform the restart.

  • Phase 4.  For an initial start or initial node restart, the redo log files are created. The number of these files is equal to NoOfFragmentLogFiles.

    For a system restart:

    • Read schema or schemas.

    • Read data from the local checkpoint.

    • Apply all redo information until the latest restorable global checkpoint has been reached.

    For a node restart, find the tail of the redo log.

  • Phase 5.  Most of the database-related portion of a data node start is performed during this phase. For an initial start or system restart, a local checkpoint is executed, followed by a global checkpoint. Periodic checks of memory usage begin during this phase, and any required node takeovers are performed.

  • Phase 6.  In this phase, node groups are defined and set up.

  • Phase 7.  The arbitrator node is selected and begins to function. The next backup ID is set, as is the backup disk write speed. Nodes reaching this start phase are marked as Started. It is now possible for API nodes (including SQL nodes) to connect to the cluster.

  • Phase 8.  If this is a system restart, all indexes are rebuilt (by DBDIH).

  • Phase 9.  The node internal startup variables are reset.

  • Phase 100 (OBSOLETE).  Formerly, it was at this point during a node restart or initial node restart that API nodes could connect to the node and begin to receive events. Currently, this phase is empty.

  • Phase 101.  At this point in a node restart or initial node restart, event delivery is handed over to the node joining the cluster. The newly-joined node takes over responsibility for delivering its primary data to subscribers. This phase is also referred to as SUMA handover phase.

After this process is completed for an initial start or system restart, transaction handling is enabled. For a node restart or initial node restart, completion of the startup process means that the node may now act as a transaction coordinator.

23.5.5 Performing a Rolling Restart of an NDB Cluster

This section discusses how to perform a rolling restart of an NDB Cluster installation, so called because it involves stopping and starting (or restarting) each node in turn, so that the cluster itself remains operational. This is often done as part of a rolling upgrade or rolling downgrade, where high availability of the cluster is mandatory and no downtime of the cluster as a whole is permissible. Where we refer to upgrades, the information provided here also generally applies to downgrades as well.

There are a number of reasons why a rolling restart might be desirable. These are described in the next few paragraphs.

Configuration change.  To make a change in the cluster's configuration, such as adding an SQL node to the cluster, or setting a configuration parameter to a new value.

NDB Cluster software upgrade or downgrade.  To upgrade the cluster to a newer version of the NDB Cluster software (or to downgrade it to an older version). This is usually referred to as a rolling upgrade (or rolling downgrade, when reverting to an older version of NDB Cluster).

Change on node host.  To make changes in the hardware or operating system on which one or more NDB Cluster node processes are running.

System reset (cluster reset).  To reset the cluster because it has reached an undesirable state. In such cases it is often desirable to reload the data and metadata of one or more data nodes. This can be done in any of three ways:

Resource Recovery.  To free memory previously allocated to a table by successive INSERT and DELETE operations, for re-use by other NDB Cluster tables.

The process for performing a rolling restart may be generalized as follows:

  1. Stop all cluster management nodes (ndb_mgmd processes), reconfigure them, then restart them. (See Rolling restarts with multiple management servers.)

  2. Stop, reconfigure, then restart each cluster data node (ndbd process) in turn.

    Some node configuration parameters can be updated by issuing RESTART for each of the data nodes in the ndb_mgm client following the previous step. Other parameters require that the data node be stopped completely using the management client STOP command, then started again from a system shell by invoking the ndbd or ndbmtd executable as appropriate. (A shell command such as kill can also be used on most Unix systems to stop a data node process, but the STOP command is preferred and usually simpler.)

    Note

    On Windows, you can also use SC STOP and SC START commands, NET STOP and NET START commands, or the Windows Service Manager to stop and start nodes which have been installed as Windows services (see Section 23.2.2.4, “Installing NDB Cluster Processes as Windows Services”).

    The type of restart required is indicated in the documentation for each node configuration parameter. See Section 23.3.3, “NDB Cluster Configuration Files”.

  3. Stop, reconfigure, then restart each cluster SQL node (mysqld process) in turn.

NDB Cluster supports a somewhat flexible order for upgrading nodes. When upgrading an NDB Cluster, you may upgrade API nodes (including SQL nodes) before upgrading the management nodes, data nodes, or both. In other words, you are permitted to upgrade the API and SQL nodes in any order. This is subject to the following provisions:

  • This functionality is intended for use as part of an online upgrade only. A mix of node binaries from different NDB Cluster releases is neither intended nor supported for continuous, long-term use in a production setting.

  • All management nodes must be upgraded before any data nodes are upgraded. This remains true regardless of the order in which you upgrade the cluster's API and SQL nodes.

  • Features specific to the new version must not be used until all management nodes and data nodes have been upgraded.

    This also applies to any MySQL Server version change that may apply, in addition to the NDB engine version change, so do not forget to take this into account when planning the upgrade. (This is true for online upgrades of NDB Cluster in general.)

It is not possible for any API node to perform schema operations (such as data definition statements) during a node restart. Due in part to this limitation, schema operations are also not supported during an online upgrade or downgrade.

Rolling restarts with multiple management servers.  When performing a rolling restart of an NDB Cluster with multiple management nodes, you should keep in mind that ndb_mgmd checks to see if any other management node is running, and, if so, tries to use that node's configuration data. To keep this from occurring, and to force ndb_mgmd to reread its configuration file, perform the following steps:

  1. Stop all NDB Cluster ndb_mgmd processes.

  2. Update all config.ini files.

  3. Start a single ndb_mgmd with --reload, --initial, or both options as desired.

  4. If you started the first ndb_mgmd with the --initial option, you must also start any remaining ndb_mgmd processes using --initial.

    Regardless of any other options used when starting the first ndb_mgmd, you should not start any remaining ndb_mgmd processes after the first one using --reload.

  5. Complete the rolling restarts of the data nodes and API nodes as normal.

When performing a rolling restart to update the cluster's configuration, you can use the config_generation column of the ndbinfo.nodes table to keep track of which data nodes have been successfully restarted with the new configuration. See Section 23.5.14.38, “The ndbinfo nodes Table”.

23.5.6 NDB Cluster Single User Mode

Single user mode enables the database administrator to restrict access to the database system to a single API node, such as a MySQL server (SQL node) or an instance of ndb_restore. When entering single user mode, connections to all other API nodes are closed gracefully and all running transactions are aborted. No new transactions are permitted to start.

Once the cluster has entered single user mode, only the designated API node is granted access to the database.

You can use the ALL STATUS command in the ndb_mgm client to see when the cluster has entered single user mode. You can also check the status column of the ndbinfo.nodes table (see Section 23.5.14.38, “The ndbinfo nodes Table”, for more information).

Example:

ndb_mgm> ENTER SINGLE USER MODE 5

After this command has executed and the cluster has entered single user mode, the API node whose node ID is 5 becomes the cluster's only permitted user.

The node specified in the preceding command must be an API node; attempting to specify any other type of node is rejected.

Note

When the preceding command is invoked, all transactions running on the designated node are aborted, the connection is closed, and the server must be restarted.

The command EXIT SINGLE USER MODE changes the state of the cluster's data nodes from single user mode to normal mode. API nodes—such as MySQL Servers—waiting for a connection (that is, waiting for the cluster to become ready and available), are again permitted to connect. The API node denoted as the single-user node continues to run (if still connected) during and after the state change.

Example:

ndb_mgm> EXIT SINGLE USER MODE

There are two recommended ways to handle a node failure when running in single user mode:

  • Method 1:

    1. Finish all single user mode transactions

    2. Issue the EXIT SINGLE USER MODE command

    3. Restart the cluster's data nodes

  • Method 2:

    Restart storage nodes prior to entering single user mode.

23.5.7 Adding NDB Cluster Data Nodes Online

This section describes how to add NDB Cluster data nodes online—that is, without needing to shut down the cluster completely and restart it as part of the process.

Important

Currently, you must add new data nodes to an NDB Cluster as part of a new node group. In addition, it is not possible to change the number of fragment replicas (or the number of nodes per node group) online.

23.5.7.1 Adding NDB Cluster Data Nodes Online: General Issues

This section provides general information about the behavior of and current limitations in adding NDB Cluster nodes online.

Redistribution of Data.  The ability to add new nodes online includes a means to reorganize NDBCLUSTER table data and indexes so that they are distributed across all data nodes, including the new ones, by means of the ALTER TABLE ... REORGANIZE PARTITION statement. Table reorganization of both in-memory and Disk Data tables is supported. This redistribution does not currently include unique indexes (only ordered indexes are redistributed).

The redistribution for NDBCLUSTER tables already existing before the new data nodes were added is not automatic, but can be accomplished using simple SQL statements in mysql or another MySQL client application. However, all data and indexes added to tables created after a new node group has been added are distributed automatically among all cluster data nodes, including those added as part of the new node group.

Partial starts.  It is possible to add a new node group without all of the new data nodes being started. It is also possible to add a new node group to a degraded cluster—that is, a cluster that is only partially started, or where one or more data nodes are not running. In the latter case, the cluster must have enough nodes running to be viable before the new node group can be added.

Effects on ongoing operations.  Normal DML operations using NDB Cluster data are not prevented by the creation or addition of a new node group, or by table reorganization. However, it is not possible to perform DDL concurrently with table reorganization—that is, no other DDL statements can be issued while an ALTER TABLE ... REORGANIZE PARTITION statement is executing. In addition, during the execution of ALTER TABLE ... REORGANIZE PARTITION (or the execution of any other DDL statement), it is not possible to restart cluster data nodes.

Failure handling.  Failures of data nodes during node group creation and table reorganization are handled as shown in the following table:

Table 23.65 Data node failure handling during node group creation and table reorganization

Failure during Failure in Old data node Failure in New data node System Failure
Node group creation
  • If a node other than the master fails:  The creation of the node group is always rolled forward.

  • If the master fails: 

    • If the internal commit point has been reached:  The creation of the node group is rolled forward.

    • If the internal commit point has not yet been reached.  The creation of the node group is rolled back

  • If a node other than the master fails:  The creation of the node group is always rolled forward.

  • If the master fails: 

    • If the internal commit point has been reached:  The creation of the node group is rolled forward.

    • If the internal commit point has not yet been reached.  The creation of the node group is rolled back

  • If the execution of CREATE NODEGROUP has reached the internal commit point:  When restarted, the cluster includes the new node group. Otherwise it without.

  • If the execution of CREATE NODEGROUP has not yet reached the internal commit point:  When restarted, the cluster does not include the new node group.

Table reorganization
  • If a node other than the master fails:  The table reorganization is always rolled forward.

  • If the master fails: 

    • If the internal commit point has been reached:  The table reorganization is rolled forward.

    • If the internal commit point has not yet been reached.  The table reorganization is rolled back.

  • If a node other than the master fails:  The table reorganization is always rolled forward.

  • If the master fails: 

    • If the internal commit point has been reached:  The table reorganization is rolled forward.

    • If the internal commit point has not yet been reached.  The table reorganization is rolled back.

  • If the execution of an ALTER TABLE ... REORGANIZE PARTITION statement has reached the internal commit point:  When the cluster is restarted, the data and indexes belonging to table are distributed using the new data nodes.

  • If the execution of an ALTER TABLE ... REORGANIZE PARTITION statement has not yet reached the internal commit point:  When the cluster is restarted, the data and indexes belonging to table are distributed using only the old data nodes.


Dropping node groups.  The ndb_mgm client supports a DROP NODEGROUP command, but it is possible to drop a node group only when no data nodes in the node group contain any data. Since there is currently no way to empty a specific data node or node group, this command works only the following two cases:

  1. After issuing CREATE NODEGROUP in the ndb_mgm client, but before issuing any ALTER TABLE ... REORGANIZE PARTITION statements in the mysql client.

  2. After dropping all NDBCLUSTER tables using DROP TABLE.

    TRUNCATE TABLE does not work for this purpose because the data nodes continue to store the table definitions.

23.5.7.2 Adding NDB Cluster Data Nodes Online: Basic procedure

In this section, we list the basic steps required to add new data nodes to an NDB Cluster. This procedure applies whether you are using ndbd or ndbmtd binaries for the data node processes. For a more detailed example, see Section 23.5.7.3, “Adding NDB Cluster Data Nodes Online: Detailed Example”.

Assuming that you already have a running NDB Cluster, adding data nodes online requires the following steps:

  1. Edit the cluster configuration config.ini file, adding new [ndbd] sections corresponding to the nodes to be added. In the case where the cluster uses multiple management servers, these changes need to be made to all config.ini files used by the management servers.

    You must be careful that node IDs for any new data nodes added in the config.ini file do not overlap node IDs used by existing nodes. In the event that you have API nodes using dynamically allocated node IDs and these IDs match node IDs that you want to use for new data nodes, it is possible to force any such API nodes to migrate, as described later in this procedure.

  2. Perform a rolling restart of all NDB Cluster management servers.

    Important

    All management servers must be restarted with the --reload or --initial option to force the reading of the new configuration.

  3. Perform a rolling restart of all existing NDB Cluster data nodes. It is not necessary (or usually even desirable) to use --initial when restarting the existing data nodes.

    If you are using API nodes with dynamically allocated IDs matching any node IDs that you wish to assign to new data nodes, you must restart all API nodes (including SQL nodes) before restarting any of the data nodes processes in this step. This causes any API nodes with node IDs that were previously not explicitly assigned to relinquish those node IDs and acquire new ones.

  4. Perform a rolling restart of any SQL or API nodes connected to the NDB Cluster.

  5. Start the new data nodes.

    The new data nodes may be started in any order. They can also be started concurrently, as long as they are started after the rolling restarts of all existing data nodes have been completed, and before proceeding to the next step.

  6. Execute one or more CREATE NODEGROUP commands in the NDB Cluster management client to create the new node group or node groups to which the new data nodes belong.

  7. Redistribute the cluster's data among all data nodes, including the new ones. Normally this is done by issuing an ALTER TABLE ... ALGORITHM=INPLACE, REORGANIZE PARTITION statement in the mysql client for each NDBCLUSTER table.

    Exception: For tables created using the MAX_ROWS option, this statement does not work; instead, use ALTER TABLE ... ALGORITHM=INPLACE MAX_ROWS=... to reorganize such tables. You should also bear in mind that using MAX_ROWS to set the number of partitions in this fashion is deprecated, and you should use PARTITION_BALANCE instead; see Section 13.1.20.11, “Setting NDB_TABLE Options”, for more information.

    Note

    This needs to be done only for tables already existing at the time the new node group is added. Data in tables created after the new node group is added is distributed automatically; however, data added to any given table tbl that existed before the new nodes were added is not distributed using the new nodes until that table has been reorganized.

  8. ALTER TABLE ... REORGANIZE PARTITION ALGORITHM=INPLACE reorganizes partitions but does not reclaim the space freed on the old nodes. You can do this by issuing, for each NDBCLUSTER table, an OPTIMIZE TABLE statement in the mysql client.

    This works for space used by variable-width columns of in-memory NDB tables. OPTIMIZE TABLE is not supported for fixed-width columns of in-memory tables; it is also not supported for Disk Data tables.

You can add all the nodes desired, then issue several CREATE NODEGROUP commands in succession to add the new node groups to the cluster.

23.5.7.3 Adding NDB Cluster Data Nodes Online: Detailed Example

In this section we provide a detailed example illustrating how to add new NDB Cluster data nodes online, starting with an NDB Cluster having 2 data nodes in a single node group and concluding with a cluster having 4 data nodes in 2 node groups.

Starting configuration.  For purposes of illustration, we assume a minimal configuration, and that the cluster uses a config.ini file containing only the following information:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21
Note

We have left a gap in the sequence between data node IDs and other nodes. This make it easier later to assign node IDs that are not already in use to data nodes which are newly added.

We also assume that you have already started the cluster using the appropriate command line or my.cnf options, and that running SHOW in the management client produces output similar to what is shown here:

-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=2    @198.51.100.2  (8.0.23-ndb-8.0.23, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (8.0.23-ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (8.0.23-ndb-8.0.23)
id=21   @198.51.100.21  (8.0.23-ndb-8.0.23)

Finally, we assume that the cluster contains a single NDBCLUSTER table created as shown here:

USE n;

CREATE TABLE ips (
    id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    country_code CHAR(2) NOT NULL,
    type CHAR(4) NOT NULL,
    ip_address VARCHAR(15) NOT NULL,
    addresses BIGINT UNSIGNED DEFAULT NULL,
    date BIGINT UNSIGNED DEFAULT NULL
)   ENGINE NDBCLUSTER;

The memory usage and related information shown later in this section was generated after inserting approximately 50000 rows into this table.

Note

In this example, we show the single-threaded ndbd being used for the data node processes. You can also apply this example, if you are using the multithreaded ndbmtd by substituting ndbmtd for ndbd wherever it appears in the steps that follow.

Step 1: Update configuration file.  Open the cluster global configuration file in a text editor and add [ndbd] sections corresponding to the 2 new data nodes. (We give these data nodes IDs 3 and 4, and assume that they are to be run on host machines at addresses 198.51.100.3 and 198.51.100.4, respectively.) After you have added the new sections, the contents of the config.ini file should look like what is shown here, where the additions to the file are shown in bold type:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[ndbd]
Id = 3
HostName = 198.51.100.3

[ndbd]
Id = 4
HostName = 198.51.100.4

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21

Once you have made the necessary changes, save the file.

Step 2: Restart the management server.  Restarting the cluster management server requires that you issue separate commands to stop the management server and then to start it again, as follows:

  1. Stop the management server using the management client STOP command, as shown here:

    ndb_mgm> 10 STOP
    Node 10 has shut down.
    Disconnecting to allow Management Server to shutdown
    
    shell>
    
  2. Because shutting down the management server causes the management client to terminate, you must start the management server from the system shell. For simplicity, we assume that config.ini is in the same directory as the management server binary, but in practice, you must supply the correct path to the configuration file. You must also supply the --reload or --initial option so that the management server reads the new configuration from the file rather than its configuration cache. If your shell's current directory is also the same as the directory where the management server binary is located, then you can invoke the management server as shown here:

    shell> ndb_mgmd -f config.ini --reload
    2008-12-08 17:29:23 [MgmSrvr] INFO     -- NDB Cluster Management Server. 8.0.23-ndb-8.0.23
    2008-12-08 17:29:23 [MgmSrvr] INFO     -- Reading cluster configuration from 'config.ini'
    

If you check the output of SHOW in the management client after restarting the ndb_mgm process, you should now see something like this:

-- NDB Cluster -- Management Client --
ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=2    @198.51.100.2  (8.0.23-ndb-8.0.23, Nodegroup: 0)
id=3 (not connected, accepting connect from 198.51.100.3)
id=4 (not connected, accepting connect from 198.51.100.4)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (8.0.23-ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (8.0.23-ndb-8.0.23)
id=21   @198.51.100.21  (8.0.23-ndb-8.0.23)

Step 3: Perform a rolling restart of the existing data nodes.  This step can be accomplished entirely within the cluster management client using the RESTART command, as shown here:

ndb_mgm> 1 RESTART
Node 1: Node shutdown initiated
Node 1: Node shutdown completed, restarting, no start.
Node 1 is being restarted

ndb_mgm> Node 1: Start initiated (version 8.0.23)
Node 1: Started (version 8.0.23)

ndb_mgm> 2 RESTART
Node 2: Node shutdown initiated
Node 2: Node shutdown completed, restarting, no start.
Node 2 is being restarted

ndb_mgm> Node 2: Start initiated (version 8.0.23)

ndb_mgm> Node 2: Started (version 8.0.23)
Important

After issuing each X RESTART command, wait until the management client reports Node X: Started (version ...) before proceeding any further.

You can verify that all existing data nodes were restarted using the updated configuration by checking the ndbinfo.nodes table in the mysql client.

Step 4: Perform a rolling restart of all cluster API nodes.  Shut down and restart each MySQL server acting as an SQL node in the cluster using mysqladmin shutdown followed by mysqld_safe (or another startup script). This should be similar to what is shown here, where password is the MySQL root password for a given MySQL server instance:

shell> mysqladmin -uroot -ppassword shutdown
081208 20:19:56 mysqld_safe mysqld from pid file
/usr/local/mysql/var/tonfisk.pid ended
shell> mysqld_safe --ndbcluster --ndb-connectstring=198.51.100.10 &
081208 20:20:06 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
081208 20:20:06 mysqld_safe Starting mysqld daemon with databases
from /usr/local/mysql/var

Of course, the exact input and output depend on how and where MySQL is installed on the system, as well as which options you choose to start it (and whether or not some or all of these options are specified in a my.cnf file).

Step 5: Perform an initial start of the new data nodes.  From a system shell on each of the hosts for the new data nodes, start the data nodes as shown here, using the --initial option:

shell> ndbd -c 198.51.100.10 --initial
Note

Unlike the case with restarting the existing data nodes, you can start the new data nodes concurrently; you do not need to wait for one to finish starting before starting the other.

Wait until both of the new data nodes have started before proceeding with the next step. Once the new data nodes have started, you can see in the output of the management client SHOW command that they do not yet belong to any node group (as indicated with bold type here):

ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=2    @198.51.100.2  (8.0.23-ndb-8.0.23, Nodegroup: 0)
id=3    @198.51.100.3  (8.0.23-ndb-8.0.23, no nodegroup)
id=4    @198.51.100.4  (8.0.23-ndb-8.0.23, no nodegroup)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (8.0.23-ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (8.0.23-ndb-8.0.23)
id=21   @198.51.100.21  (8.0.23-ndb-8.0.23)

Step 6: Create a new node group.  You can do this by issuing a CREATE NODEGROUP command in the cluster management client. This command takes as its argument a comma-separated list of the node IDs of the data nodes to be included in the new node group, as shown here:

ndb_mgm> CREATE NODEGROUP 3,4
Nodegroup 1 created

By issuing SHOW again, you can verify that data nodes 3 and 4 have joined the new node group (again indicated in bold type):

ndb_mgm> SHOW
Connected to Management Server at: 198.51.100.10:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @198.51.100.1  (8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=2    @198.51.100.2  (8.0.23-ndb-8.0.23, Nodegroup: 0)
id=3    @198.51.100.3  (8.0.23-ndb-8.0.23, Nodegroup: 1)
id=4    @198.51.100.4  (8.0.23-ndb-8.0.23, Nodegroup: 1)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @198.51.100.10  (8.0.23-ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=20   @198.51.100.20  (8.0.23-ndb-8.0.23)
id=21   @198.51.100.21  (8.0.23-ndb-8.0.23)

Step 7: Redistribute cluster data.  When a node group is created, existing data and indexes are not automatically distributed to the new node group's data nodes, as you can see by issuing the appropriate REPORT command in the management client:

ndb_mgm> ALL REPORT MEMORY

Node 1: Data usage is 5%(177 32K pages of total 3200)
Node 1: Index usage is 0%(108 8K pages of total 12832)
Node 2: Data usage is 5%(177 32K pages of total 3200)
Node 2: Index usage is 0%(108 8K pages of total 12832)
Node 3: Data usage is 0%(0 32K pages of total 3200)
Node 3: Index usage is 0%(0 8K pages of total 12832)
Node 4: Data usage is 0%(0 32K pages of total 3200)
Node 4: Index usage is 0%(0 8K pages of total 12832)

By using ndb_desc with the -p option, which causes the output to include partitioning information, you can see that the table still uses only 2 partitions (in the Per partition info section of the output, shown here in bold text):

shell> ndb_desc -c 198.51.100.10 -d n ips -p
-- ips --
Version: 1
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 340
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 2
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY

-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex

-- Per partition info --
Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
0           26086       26086         1572864             557056
1           26329       26329         1605632             557056

NDBT_ProgramExit: 0 - OK

You can cause the data to be redistributed among all of the data nodes by performing, for each NDB table, an ALTER TABLE ... ALGORITHM=INPLACE, REORGANIZE PARTITION statement in the mysql client.

Important

ALTER TABLE ... ALGORITHM=INPLACE, REORGANIZE PARTITION does not work on tables that were created with the MAX_ROWS option. Instead, use ALTER TABLE ... ALGORITHM=INPLACE, MAX_ROWS=... to reorganize such tables.

Keep in mind that using MAX_ROWS to set the number of partitions per table is deprecated, and you should use PARTITION_BALANCE instead; see Section 13.1.20.11, “Setting NDB_TABLE Options”, for more information.

After issuing the statement ALTER TABLE ips ALGORITHM=INPLACE, REORGANIZE PARTITION, you can see using ndb_desc that the data for this table is now stored using 4 partitions, as shown here (with the relevant portions of the output in bold type):

shell> ndb_desc -c 198.51.100.10 -d n ips -p
-- ips --
Version: 16777217
Fragment type: 9
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 6
Number of primary keys: 1
Length of frm data: 341
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
FragmentCount: 4
TableStatus: Retrieved
-- Attributes --
id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
addresses Bigunsigned NULL AT=FIXED ST=MEMORY
date Bigunsigned NULL AT=FIXED ST=MEMORY

-- Indexes --
PRIMARY KEY(id) - UniqueHashIndex
PRIMARY(id) - OrderedIndex

-- Per partition info --
Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
0           12981       52296         1572864             557056
1           13236       52515         1605632             557056
2           13105       13105         819200              294912
3           13093       13093         819200              294912

NDBT_ProgramExit: 0 - OK
Note

Normally, ALTER TABLE table_name [ALGORITHM=INPLACE,] REORGANIZE PARTITION is used with a list of partition identifiers and a set of partition definitions to create a new partitioning scheme for a table that has already been explicitly partitioned. Its use here to redistribute data onto a new NDB Cluster node group is an exception in this regard; when used in this way, no other keywords or identifiers follow REORGANIZE PARTITION.

For more information, see Section 13.1.9, “ALTER TABLE Statement”.

In addition, for each table, the ALTER TABLE statement should be followed by an OPTIMIZE TABLE to reclaim wasted space. You can obtain a list of all NDBCLUSTER tables using the following query against the INFORMATION_SCHEMA.TABLES table:

SELECT TABLE_SCHEMA, TABLE_NAME
    FROM INFORMATION_SCHEMA.TABLES
    WHERE ENGINE = 'NDBCLUSTER';
Note

The INFORMATION_SCHEMA.TABLES.ENGINE value for an NDB Cluster table is always NDBCLUSTER, regardless of whether the CREATE TABLE statement used to create the table (or ALTER TABLE statement used to convert an existing table from a different storage engine) used NDB or NDBCLUSTER in its ENGINE option.

You can see after performing these statements in the output of ALL REPORT MEMORY that the data and indexes are now redistributed between all cluster data nodes, as shown here:

ndb_mgm> ALL REPORT MEMORY

Node 1: Data usage is 5%(176 32K pages of total 3200)
Node 1: Index usage is 0%(76 8K pages of total 12832)
Node 2: Data usage is 5%(176 32K pages of total 3200)
Node 2: Index usage is 0%(76 8K pages of total 12832)
Node 3: Data usage is 2%(80 32K pages of total 3200)
Node 3: Index usage is 0%(51 8K pages of total 12832)
Node 4: Data usage is 2%(80 32K pages of total 3200)
Node 4: Index usage is 0%(50 8K pages of total 12832)
Note

Since only one DDL operation on NDBCLUSTER tables can be executed at a time, you must wait for each ALTER TABLE ... REORGANIZE PARTITION statement to finish before issuing the next one.

It is not necessary to issue ALTER TABLE ... REORGANIZE PARTITION statements for NDBCLUSTER tables created after the new data nodes have been added; data added to such tables is distributed among all data nodes automatically. However, in NDBCLUSTER tables that existed prior to the addition of the new nodes, neither existing nor new data is distributed using the new nodes until these tables have been reorganized using ALTER TABLE ... REORGANIZE PARTITION.

Alternative procedure, without rolling restart.  It is possible to avoid the need for a rolling restart by configuring the extra data nodes, but not starting them, when first starting the cluster. We assume, as before, that you wish to start with two data nodes—nodes 1 and 2—in one node group and later to expand the cluster to four data nodes, by adding a second node group consisting of nodes 3 and 4:

[ndbd default]
DataMemory = 100M
IndexMemory = 100M
NoOfReplicas = 2
DataDir = /usr/local/mysql/var/mysql-cluster

[ndbd]
Id = 1
HostName = 198.51.100.1

[ndbd]
Id = 2
HostName = 198.51.100.2

[ndbd]
Id = 3
HostName = 198.51.100.3
Nodegroup = 65536

[ndbd]
Id = 4
HostName = 198.51.100.4
Nodegroup = 65536

[mgm]
HostName = 198.51.100.10
Id = 10

[api]
Id=20
HostName = 198.51.100.20

[api]
Id=21
HostName = 198.51.100.21

The data nodes to be brought online at a later time (nodes 3 and 4) can be configured with NodeGroup = 65536, in which case nodes 1 and 2 can each be started as shown here:

shell> ndbd -c 198.51.100.10 --initial

The data nodes configured with NodeGroup = 65536 are treated by the management server as though you had started nodes 1 and 2 using --nowait-nodes=3,4 after waiting for a period of time determined by the setting for the StartNoNodeGroupTimeout data node configuration parameter. By default, this is 15 seconds (15000 milliseconds).

Note

StartNoNodegroupTimeout must be the same for all data nodes in the cluster; for this reason, you should always set it in the [ndbd default] section of the config.ini file, rather than for individual data nodes.

When you are ready to add the second node group, you need only perform the following additional steps:

  1. Start data nodes 3 and 4, invoking the data node process once for each new node:

    shell> ndbd -c 198.51.100.10 --initial
    
  2. Issue the appropriate CREATE NODEGROUP command in the management client:

    ndb_mgm> CREATE NODEGROUP 3,4
    
  3. In the mysql client, issue ALTER TABLE ... REORGANIZE PARTITION and OPTIMIZE TABLE statements for each existing NDBCLUSTER table. (As noted elsewhere in this section, existing NDB Cluster tables cannot use the new nodes for data distribution until this has been done.)

23.5.8 Online Backup of NDB Cluster

The next few sections describe how to prepare for and then to create an NDB Cluster backup using the functionality for this purpose found in the ndb_mgm management client. To distinguish this type of backup from a backup made using mysqldump, we sometimes refer to it as a native NDB Cluster backup. (For information about the creation of backups with mysqldump, see Section 4.5.4, “mysqldump — A Database Backup Program”.) Restoration of NDB Cluster backups is done using the ndb_restore utility provided with the NDB Cluster distribution; for information about ndb_restore and its use in restoring NDB Cluster backups, see Section 23.4.23, “ndb_restore — Restore an NDB Cluster Backup”.

Starting with NDB 8.0.16, it is possible to create backups using multiple LDMs to achieve parallelism on the data nodes. See Section 23.5.8.5, “Taking an NDB Backup with Parallel Data Nodes”.

23.5.8.1 NDB Cluster Backup Concepts

A backup is a snapshot of the database at a given time. The backup consists of three main parts:

  • Metadata.  The names and definitions of all database tables

  • Table records.  The data actually stored in the database tables at the time that the backup was made

  • Transaction log.  A sequential record telling how and when data was stored in the database

Each of these parts is saved on all nodes participating in the backup. During backup, each node saves these three parts into three files on disk:

  • BACKUP-backup_id.node_id.ctl

    A control file containing control information and metadata. Each node saves the same table definitions (for all tables in the cluster) to its own version of this file.

  • BACKUP-backup_id-0.node_id.data

    A data file containing the table records, which are saved on a per-fragment basis. That is, different nodes save different fragments during the backup. The file saved by each node starts with a header that states the tables to which the records belong. Following the list of records there is a footer containing a checksum for all records.

  • BACKUP-backup_id.node_id.log

    A log file containing records of committed transactions. Only transactions on tables stored in the backup are stored in the log. Nodes involved in the backup save different records because different nodes host different database fragments.

In the listing just shown, backup_id stands for the backup identifier and node_id is the unique identifier for the node creating the file.

The location of the backup files is determined by the BackupDataDir parameter.

23.5.8.2 Using The NDB Cluster Management Client to Create a Backup

Before starting a backup, make sure that the cluster is properly configured for performing one. (See Section 23.5.8.3, “Configuration for NDB Cluster Backups”.)

The START BACKUP command is used to create a backup:

START BACKUP [backup_id]
    [encryption_option]
    [wait_option]
    [snapshot_option]

encryption_option:
ENCRYPT PASSWORD=password

password:
{'password_string' | "password_string"}

wait_option:
WAIT {STARTED | COMPLETED} | NOWAIT

snapshot_option:
SNAPSHOTSTART | SNAPSHOTEND

Successive backups are automatically identified sequentially, so the backup_id, an integer greater than or equal to 1, is optional; if it is omitted, the next available value is used. If an existing backup_id value is used, the backup fails with the error Backup failed: file already exists. If used, the backup_id must follow START BACKUP immediately, before any other options are used.

NDB 8.0.22 and later supports the creation of encrypted backups using ENCRYPT PASSWORD=password; the password must meet all of the following requirements:

  • Uses any of the printable ASCII characters except !, ', ", $, %, \, and ^

  • Is no more than 256 characters in length

  • Is enclosed by single or double quotation marks

It is possible to use an empty password ('' or ""), but this is not recommended.

An encrypted backup can be decrypted using any of the following commands:

See the descriptions of these programs for more information, such as additional options that may be required.

The wait_option can be used to determine when control is returned to the management client after a START BACKUP command is issued, as shown in the following list:

  • If NOWAIT is specified, the management client displays a prompt immediately, as seen here:

    ndb_mgm> START BACKUP NOWAIT
    ndb_mgm>
    

    In this case, the management client can be used even while it prints progress information from the backup process.

  • With WAIT STARTED the management client waits until the backup has started before returning control to the user, as shown here:

    ndb_mgm> START BACKUP WAIT STARTED
    Waiting for started, this may take several minutes
    Node 2: Backup 3 started from node 1
    ndb_mgm>
    
  • WAIT COMPLETED causes the management client to wait until the backup process is complete before returning control to the user.

WAIT COMPLETED is the default.

A snapshot_option can be used to determine whether the backup matches the state of the cluster when START BACKUP was issued, or when it was completed. SNAPSHOTSTART causes the backup to match the state of the cluster when the backup began; SNAPSHOTEND causes the backup to reflect the state of the cluster when the backup was finished. SNAPSHOTEND is the default, and matches the behavior found in previous NDB Cluster releases.

Note

If you use the SNAPSHOTSTART option with START BACKUP, and the CompressedBackup parameter is enabled, only the data and control files are compressed—the log file is not compressed.

If both a wait_option and a snapshot_option are used, they may be specified in either order. For example, all of the following commands are valid, assuming that there is no existing backup having 4 as its ID:

START BACKUP WAIT STARTED SNAPSHOTSTART
START BACKUP SNAPSHOTSTART WAIT STARTED
START BACKUP 4 WAIT COMPLETED SNAPSHOTSTART
START BACKUP SNAPSHOTEND WAIT COMPLETED
START BACKUP 4 NOWAIT SNAPSHOTSTART

The procedure for creating a backup consists of the following steps:

  1. Start the management client (ndb_mgm), if it not running already.

  2. Execute the START BACKUP command. This produces several lines of output indicating the progress of the backup, as shown here:

    ndb_mgm> START BACKUP
    Waiting for completed, this may take several minutes
    Node 2: Backup 1 started from node 1
    Node 2: Backup 1 started from node 1 completed
     StartGCP: 177 StopGCP: 180
     #Records: 7362 #LogRecords: 0
     Data: 453648 bytes Log: 0 bytes
    ndb_mgm>
    
  3. When the backup has started the management client displays this message:

    Backup backup_id started from node node_id
    

    backup_id is the unique identifier for this particular backup. This identifier is saved in the cluster log, if it has not been configured otherwise. node_id is the identifier of the management server that is coordinating the backup with the data nodes. At this point in the backup process the cluster has received and processed the backup request. It does not mean that the backup has finished. An example of this statement is shown here:

    Node 2: Backup 1 started from node 1
    
  4. The management client indicates with a message like this one that the backup has started:

    Backup backup_id started from node node_id completed
    

    As is the case for the notification that the backup has started, backup_id is the unique identifier for this particular backup, and node_id is the node ID of the management server that is coordinating the backup with the data nodes. This output is accompanied by additional information including relevant global checkpoints, the number of records backed up, and the size of the data, as shown here:

    Node 2: Backup 1 started from node 1 completed
     StartGCP: 177 StopGCP: 180
     #Records: 7362 #LogRecords: 0
     Data: 453648 bytes Log: 0 bytes
    

It is also possible to perform a backup from the system shell by invoking ndb_mgm with the -e or --execute option, as shown in this example:

shell> ndb_mgm -e "START BACKUP 6 WAIT COMPLETED SNAPSHOTSTART"

When using START BACKUP in this way, you must specify the backup ID.

Cluster backups are created by default in the BACKUP subdirectory of the DataDir on each data node. This can be overridden for one or more data nodes individually, or for all cluster data nodes in the config.ini file using the BackupDataDir configuration parameter. The backup files created for a backup with a given backup_id are stored in a subdirectory named BACKUP-backup_id in the backup directory.

Cancelling backups.  To cancel or abort a backup that is already in progress, perform the following steps:

  1. Start the management client.

  2. Execute this command:

    ndb_mgm> ABORT BACKUP backup_id
    

    The number backup_id is the identifier of the backup that was included in the response of the management client when the backup was started (in the message Backup backup_id started from node management_node_id).

  3. The management client acknowledges the abort request with Abort of backup backup_id ordered.

    Note

    At this point, the management client has not yet received a response from the cluster data nodes to this request, and the backup has not yet actually been aborted.

  4. After the backup has been aborted, the management client reports this fact in a manner similar to what is shown here:

    Node 1: Backup 3 started from 5 has been aborted.
      Error: 1321 - Backup aborted by user request: Permanent error: User defined error
    Node 3: Backup 3 started from 5 has been aborted.
      Error: 1323 - 1323: Permanent error: Internal error
    Node 2: Backup 3 started from 5 has been aborted.
      Error: 1323 - 1323: Permanent error: Internal error
    Node 4: Backup 3 started from 5 has been aborted.
      Error: 1323 - 1323: Permanent error: Internal error
    

    In this example, we have shown sample output for a cluster with 4 data nodes, where the sequence number of the backup to be aborted is 3, and the management node to which the cluster management client is connected has the node ID 5. The first node to complete its part in aborting the backup reports that the reason for the abort was due to a request by the user. (The remaining nodes report that the backup was aborted due to an unspecified internal error.)

    Note

    There is no guarantee that the cluster nodes respond to an ABORT BACKUP command in any particular order.

    The Backup backup_id started from node management_node_id has been aborted messages mean that the backup has been terminated and that all files relating to this backup have been removed from the cluster file system.

It is also possible to abort a backup in progress from a system shell using this command:

shell> ndb_mgm -e "ABORT BACKUP backup_id"
Note

If there is no backup having the ID backup_id running when an ABORT BACKUP is issued, the management client makes no response, nor is it indicated in the cluster log that an invalid abort command was sent.

23.5.8.3 Configuration for NDB Cluster Backups

Five configuration parameters are essential for backup:

  • BackupDataBufferSize

    The amount of memory used to buffer data before it is written to disk.

  • BackupLogBufferSize

    The amount of memory used to buffer log records before these are written to disk.

  • BackupMemory

    The total memory allocated in a data node for backups. This should be the sum of the memory allocated for the backup data buffer and the backup log buffer.

  • BackupWriteSize

    The default size of blocks written to disk. This applies for both the backup data buffer and the backup log buffer.

  • BackupMaxWriteSize

    The maximum size of blocks written to disk. This applies for both the backup data buffer and the backup log buffer.

In addition, CompressedBackup causes NDB to use compression when creating and writing to backup files.

More detailed information about these parameters can be found in Backup Parameters.

You can also set a location for the backup files using the BackupDataDir configuration parameter. The default is FileSystemPath/BACKUP/BACKUP-backup_id.

In NDB 8.0.22 and later, you can enforce encryption of backup files by enabling RequireEncryptedBackup. When this parameter is set to 1, backups cannot be created without specifying ENCRYPT PASSWORD=password as part of a START BACKUP command.

23.5.8.4 NDB Cluster Backup Troubleshooting

If an error code is returned when issuing a backup request, the most likely cause is insufficient memory or disk space. You should check that there is enough memory allocated for the backup.

Important

If you have set BackupDataBufferSize and BackupLogBufferSize and their sum is greater than 4MB, then you must also set BackupMemory as well.

You should also make sure that there is sufficient space on the hard drive partition of the backup target.

NDB does not support repeatable reads, which can cause problems with the restoration process. Although the backup process is hot, restoring an NDB Cluster from backup is not a 100% hot process. This is due to the fact that, for the duration of the restore process, running transactions get nonrepeatable reads from the restored data. This means that the state of the data is inconsistent while the restore is in progress.

23.5.8.5 Taking an NDB Backup with Parallel Data Nodes

Beginning with NDB 8.0.16, it is possible to take a backup with multiple local data managers (LDMs) acting in parallel on the data nodes. For this to work, all data nodes in the cluster must use multiple LDMs, and each data node must use the same number of LDMs. This means that all data nodes must run ndbmtd (ndbd is single-threaded and thus always has only one LDM) and they must be configured to use multiple LDMs before taking the backup; ndbmtd by default runs in single-threaded mode. You can cause them to use multiple LDMs this by choosing an appropriate setting for one of the multi-threaded data node configuration parameters MaxNoOfExecutionThreads or ThreadConfig. Keep in mind that changing these parameters requires a restart of the cluster; this can be a rolling restart.

Depending on the number of LDMs and other factors, you may also need to increase NoOfFragmentLogParts. If you are using large Disk Data tables, you may also need to increase DiskPageBufferMemory. As with single-threaded backups, you also want or need to make adjustments to settings for BackupDataBufferSize, BackupMemory, and other configuration parameters relating to backups (see Backup parameters).

Once all data nodes are using multiple LDMs, you can take the parallel backup using the START BACKUP command in the NDB management client just as you would if the data nodes were running ndbd (or ndbmtd in single-threaded mode); no additional or special syntax is required, and you can specify a backup ID, wait option, or snapshot option in any combination as needed or desired.

Backups using multiple LDMs create subdirectories, one per LDM, under the directory BACKUP/BACKUP-backup_id/ (which in turn resides under the BackupDataDir) on each data node; these subdirectories are named BACKUP-backup_id-PART-1-OF-N/, BACKUP-backup_id-PART-2-OF-N/, and so on, up to BACKUP-backup_id-PART-N-OF-N/, where backup_id is the backup ID used for this backup and N is the number of LDMs per data node. Each of these subdirectories contains the usual backup files BACKUP-backup_id-0.node_id.Data, BACKUP-backup_id.node_id.ctl, and BACKUP-backup_id.node_id.log, where node_id is the node ID of this data node.

In NDB 8.0.16 and later, ndb_restore automatically checks for the presence of the subdirectories just described; if it finds them, it attempts to restore the backup in parallel. For information about restoring backups taken with multiple LDMs, see Section 23.4.23.3, “Restoring from a backup taken in parallel”.

23.5.9 MySQL Server Usage for NDB Cluster

mysqld is the traditional MySQL server process. To be used with NDB Cluster, mysqld needs to be built with support for the NDB storage engine, as it is in the precompiled binaries available from https://dev.mysql.com/downloads/. If you build MySQL from source, you must invoke CMake with the -DWITH_NDBCLUSTER=1 option to include support for NDB.

For more information about compiling NDB Cluster from source, see Section 23.2.1.4, “Building NDB Cluster from Source on Linux”, and Section 23.2.2.2, “Compiling and Installing NDB Cluster from Source on Windows”.

(For information about mysqld options and variables, in addition to those discussed in this section, which are relevant to NDB Cluster, see Section 23.3.3.9, “MySQL Server Options and Variables for NDB Cluster”.)

If the mysqld binary has been built with Cluster support, the NDBCLUSTER storage engine is still disabled by default. You can use either of two possible options to enable this engine:

  • Use --ndbcluster as a startup option on the command line when starting mysqld.

  • Insert a line containing ndbcluster in the [mysqld] section of your my.cnf file.

An easy way to verify that your server is running with the NDBCLUSTER storage engine enabled is to issue the SHOW ENGINES statement in the MySQL Monitor (mysql). You should see the value YES as the Support value in the row for NDBCLUSTER. If you see NO in this row or if there is no such row displayed in the output, you are not running an NDB-enabled version of MySQL. If you see DISABLED in this row, you need to enable it in either one of the two ways just described.

To read cluster configuration data, the MySQL server requires at a minimum three pieces of information:

  • The MySQL server's own cluster node ID

  • The host name or IP address for the management server

  • The number of the TCP/IP port on which it can connect to the management server

Node IDs can be allocated dynamically, so it is not strictly necessary to specify them explicitly.

The mysqld parameter ndb-connectstring is used to specify the connection string either on the command line when starting mysqld or in my.cnf. The connection string contains the host name or IP address where the management server can be found, as well as the TCP/IP port it uses.

In the following example, ndb_mgmd.mysql.com is the host where the management server resides, and the management server listens for cluster messages on port 1186:

shell> mysqld --ndbcluster --ndb-connectstring=ndb_mgmd.mysql.com:1186

See Section 23.3.3.3, “NDB Cluster Connection Strings”, for more information on connection strings.

Given this information, the MySQL server can act as a full participant in the cluster. (We often refer to a mysqld process running in this manner as an SQL node.) It is fully aware of all cluster data nodes as well as their status, and establishes connections to all data nodes. In this case, it is able to use any data node as a transaction coordinator and to read and update node data.

You can see in the mysql client whether a MySQL server is connected to the cluster using SHOW PROCESSLIST. If the MySQL server is connected to the cluster, and you have the PROCESS privilege, then the first row of the output is as shown here:

mysql> SHOW PROCESSLIST \G
*************************** 1. row ***************************
     Id: 1
   User: system user
   Host:
     db:
Command: Daemon
   Time: 1
  State: Waiting for event from ndbcluster
   Info: NULL
Important

To participate in an NDB Cluster, the mysqld process must be started with both the options --ndbcluster and --ndb-connectstring (or their equivalents in my.cnf). If mysqld is started with only the --ndbcluster option, or if it is unable to contact the cluster, it is not possible to work with NDB tables, nor is it possible to create any new tables regardless of storage engine. The latter restriction is a safety measure intended to prevent the creation of tables having the same names as NDB tables while the SQL node is not connected to the cluster. If you wish to create tables using a different storage engine while the mysqld process is not participating in an NDB Cluster, you must restart the server without the --ndbcluster option.

23.5.10 NDB Cluster Disk Data Tables

NDB Cluster supports storing nonindexed columns of NDB tables on disk, rather than in RAM. Column data and logging metadata are kept in data files and undo log files, conceptualized as tablespaces and log file groups, as described in the next section—see Section 23.5.10.1, “NDB Cluster Disk Data Objects”.

NDB Cluster Disk Data performance can be influenced by a number of configuration parameters. For information about these parameters and their effects, see Disk Data Configuration Parameters, and Disk Data and GCP Stop errors.

Beginning with NDB 8.0.19, you should also set the DiskDataUsingSameDisk data node configuration parameter to false when using separate disks for Disk Data files.

See also Disk Data file system parameters.

NDB 8.0.19 (and later) provides improved support when using Disk Data tables with solid-state drives, in particular those using NVMe. See the following documentation for more information:

23.5.10.1 NDB Cluster Disk Data Objects

NDB Cluster Disk Data storage is implemented using the following objects:

  • Tablespace: Acts as containers for other Disk Data objects. A tablespace contains one or more data files and one or more undo log file groups.

  • Data file: Stores column data. A data file is assigned directly to a tablespace.

  • Undo log file: Contains undo information required for rolling back transactions. Assigned to an undo log file group.

  • log file group: Contains one or more undo log files. Assigned to a tablespace.

Undo log files and data files are actual files in the file system of each data node; by default they are placed in ndb_node_id_fs in the DataDir specified in the NDB Cluster config.ini file, and where node_id is the data node's node ID. It is possible to place these elsewhere by specifying either an absolute or relative path as part of the filename when creating the undo log or data file. Statements that create these files are shown later in this section.

Undo log files are used only by Disk Data tables, and are not needed or used by NDB tables that are stored in memory only.

NDB Cluster tablespaces and log file groups are not implemented as files.

Although not all Disk Data objects are implemented as files, they all share the same namespace. This means that each Disk Data object must be uniquely named (and not merely each Disk Data object of a given type). For example, you cannot have a tablespace and a log file group both named dd1.

Assuming that you have already set up an NDB Cluster with all nodes (including management and SQL nodes), the basic steps for creating an NDB Cluster table on disk are as follows:

  1. Create a log file group, and assign one or more undo log files to it (an undo log file is also sometimes referred to as an undofile).

  2. Create a tablespace; assign the log file group, as well as one or more data files, to the tablespace.

  3. Create a Disk Data table that uses this tablespace for data storage.

Each of these tasks can be accomplished using SQL statements in the mysql client or other MySQL client application, as shown in the example that follows.

  1. We create a log file group named lg_1 using CREATE LOGFILE GROUP. This log file group is to be made up of two undo log files, which we name undo_1.log and undo_2.log, whose initial sizes are 16 MB and 12 MB, respectively. (The default initial size for an undo log file is 128 MB.) Optionally, you can also specify a size for the log file group's undo buffer, or permit it to assume the default value of 8 MB. In this example, we set the UNDO buffer's size at 2 MB. A log file group must be created with an undo log file; so we add undo_1.log to lg_1 in this CREATE LOGFILE GROUP statement:

    CREATE LOGFILE GROUP lg_1
        ADD UNDOFILE 'undo_1.log'
        INITIAL_SIZE 16M
        UNDO_BUFFER_SIZE 2M
        ENGINE NDBCLUSTER;
    

    To add undo_2.log to the log file group, use the following ALTER LOGFILE GROUP statement:

    ALTER LOGFILE GROUP lg_1
        ADD UNDOFILE 'undo_2.log'
        INITIAL_SIZE 12M
        ENGINE NDBCLUSTER;
    

    Some items of note:

    • The .log file extension used here is not required. We employ it merely to make the log files easily recognizable.

    • Every CREATE LOGFILE GROUP and ALTER LOGFILE GROUP statement must include an ENGINE option. The only permitted values for this option are NDBCLUSTER and NDB.

      Important

      There can exist at most one log file group in the same NDB Cluster at any given time.

    • When you add an undo log file to a log file group using ADD UNDOFILE 'filename', a file with the name filename is created in the ndb_node_id_fs directory within the DataDir of each data node in the cluster, where node_id is the node ID of the data node. Each undo log file is of the size specified in the SQL statement. For example, if an NDB Cluster has 4 data nodes, then the ALTER LOGFILE GROUP statement just shown creates 4 undo log files, 1 each on in the data directory of each of the 4 data nodes; each of these files is named undo_2.log and each file is 12 MB in size.

    • UNDO_BUFFER_SIZE is limited by the amount of system memory available.

    • See Section 13.1.16, “CREATE LOGFILE GROUP Statement”, and Section 13.1.6, “ALTER LOGFILE GROUP Statement”, for more information about these statements.

  2. Now we can create a tablespace—an abstract container for files used by Disk Data tables to store data. A tablespace is associated with a particular log file group; when creating a new tablespace, you must specify the log file group it uses for undo logging. You must also specify at least one data file; you can add more data files to the tablespace after the tablespace is created. It is also possible to drop data files from a tablespace (see example later in this section).

    Assume that we wish to create a tablespace named ts_1 which uses lg_1 as its log file group. We want the tablespace to contain two data files, named data_1.dat and data_2.dat, whose initial sizes are 32 MB and 48 MB, respectively. (The default value for INITIAL_SIZE is 128 MB.) We can do this using two SQL statements, as shown here:

    CREATE TABLESPACE ts_1
        ADD DATAFILE 'data_1.dat'
        USE LOGFILE GROUP lg_1
        INITIAL_SIZE 32M
        ENGINE NDBCLUSTER;
    
    ALTER TABLESPACE ts_1
        ADD DATAFILE 'data_2.dat'
        INITIAL_SIZE 48M;
    

    The CREATE TABLESPACE statement creates a tablespace ts_1 with the data file data_1.dat, and associates ts_1 with log file group lg_1. The ALTER TABLESPACE adds the second data file (data_2.dat).

    Some items of note:

    • As is the case with the .log file extension used in this example for undo log files, there is no special significance for the .dat file extension; it is used merely for easy recognition.

    • When you add a data file to a tablespace using ADD DATAFILE 'filename', a file with the name filename is created in the ndb_node_id_fs directory within the DataDir of each data node in the cluster, where node_id is the node ID of the data node. Each data file is of the size specified in the SQL statement. For example, if an NDB Cluster has 4 data nodes, then the ALTER TABLESPACE statement just shown creates 4 data files, 1 each in the data directory of each of the 4 data nodes; each of these files is named data_2.dat and each file is 48 MB in size.

    • NDB reserves 4% of each tablespace for use during data node restarts. This space is not available for storing data.

    • CREATE TABLESPACE statements must contain an ENGINE clause; only tables using the same storage engine as the tablespace can be created in the tablespace. For ALTER TABLESPACE, an ENGINE clause is accepted but is deprecated and subject to removal in a future release. For NDB tablespaces, the only permitted values for this option are NDBCLUSTER and NDB.

    • In NDB 8.0.20 and later, allocation of extents is performed in round-robin fashion among all data files used by a given tablespace.

    • For more information about the CREATE TABLESPACE and ALTER TABLESPACE statements, see Section 13.1.21, “CREATE TABLESPACE Statement”, and Section 13.1.10, “ALTER TABLESPACE Statement”.

  3. Now it is possible to create a table whose unindexed columns are stored on disk using files in tablespace ts_1:

    CREATE TABLE dt_1 (
        member_id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
        last_name VARCHAR(50) NOT NULL,
        first_name VARCHAR(50) NOT NULL,
        dob DATE NOT NULL,
        joined DATE NOT NULL,
        INDEX(last_name, first_name)
        )
        TABLESPACE ts_1 STORAGE DISK
        ENGINE NDBCLUSTER;
    

    TABLESPACE ts_1 STORAGE DISK tells the NDB storage engine to use tablespace ts_1 for data storage on disk.

    Once table ts_1 has been created as shown, you can perform INSERT, SELECT, UPDATE, and DELETE statements on it just as you would with any other MySQL table.

    It is also possible to specify whether an individual column is stored on disk or in memory by using a STORAGE clause as part of the column's definition in a CREATE TABLE or ALTER TABLE statement. STORAGE DISK causes the column to be stored on disk, and STORAGE MEMORY causes in-memory storage to be used. See Section 13.1.20, “CREATE TABLE Statement”, for more information.

You can obtain information about the NDB disk data files and undo log files just created by querying the FILES table in the INFORMATION_SCHEMA database, as shown here:

mysql> SELECT
              FILE_NAME AS File, FILE_TYPE AS Type,
              TABLESPACE_NAME AS Tablespace, TABLE_NAME AS Name,
              LOGFILE_GROUP_NAME AS 'File group',
              FREE_EXTENTS AS Free, TOTAL_EXTENTS AS Total
          FROM INFORMATION_SCHEMA.FILES
          WHERE ENGINE='ndbcluster';
+--------------+----------+------------+------+------------+------+---------+
| File         | Type     | Tablespace | Name | File group | Free | Total   |
+--------------+----------+------------+------+------------+------+---------+
| ./undo_1.log | UNDO LOG | lg_1       | NULL | lg_1       |    0 | 4194304 |
| ./undo_2.log | UNDO LOG | lg_1       | NULL | lg_1       |    0 | 3145728 |
| ./data_1.dat | DATAFILE | ts_1       | NULL | lg_1       |   32 |      32 |
| ./data_2.dat | DATAFILE | ts_1       | NULL | lg_1       |   48 |      48 |
+--------------+----------+------------+------+------------+------+---------+
4 rows in set (0.00 sec)

For more information and examples, see Section 26.15, “The INFORMATION_SCHEMA FILES Table”.

Indexing of columns implicitly stored on disk.  For table dt_1 as defined in the example just shown, only the dob and joined columns are stored on disk. This is because there are indexes on the id, last_name, and first_name columns, and so data belonging to these columns is stored in RAM. Only nonindexed columns can be held on disk; indexes and indexed column data continue to be stored in memory. This tradeoff between the use of indexes and conservation of RAM is something you must keep in mind as you design Disk Data tables.

You cannot add an index to a column that has been explicitly declared STORAGE DISK, without first changing its storage type to MEMORY; any attempt to do so fails with an error. A column which implicitly uses disk storage can be indexed; when this is done, the column's storage type is changed to MEMORY automatically. By implicitly, we mean a column whose storage type is not declared, but which is which inherited from the parent table. In the following CREATE TABLE statement (using the tablespace ts_1 defined previously), columns c2 and c3 use disk storage implicitly:

mysql> CREATE TABLE ti (
    ->     c1 INT PRIMARY KEY,
    ->     c2 INT,
    ->     c3 INT,
    ->     c4 INT
    -> )
    ->     STORAGE DISK
    ->     TABLESPACE ts_1
    ->     ENGINE NDBCLUSTER;
Query OK, 0 rows affected (1.31 sec)

Because c2, c3, and c4 are themselves not declared with STORAGE DISK, it is possible to index them. Here, we add indexes to c2 and c3, using, respectively, CREATE INDEX and ALTER TABLE:

mysql> CREATE INDEX i1 ON ti(c2);
Query OK, 0 rows affected (2.72 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> ALTER TABLE ti ADD INDEX i2(c3);
Query OK, 0 rows affected (0.92 sec)
Records: 0  Duplicates: 0  Warnings: 0

SHOW CREATE TABLE confirms that the indexes were added.

mysql> SHOW CREATE TABLE ti\G
*************************** 1. row ***************************
       Table: ti
Create Table: CREATE TABLE `ti` (
  `c1` int(11) NOT NULL,
  `c2` int(11) DEFAULT NULL,
  `c3` int(11) DEFAULT NULL,
  `c4` int(11) DEFAULT NULL,
  PRIMARY KEY (`c1`),
  KEY `i1` (`c2`),
  KEY `i2` (`c3`)
) /*!50100 TABLESPACE `ts_1` STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

You can see using ndb_desc that the indexed columns (emphasized text) now use in-memory rather than on-disk storage:

shell> ./ndb_desc -d test t1
-- t1 --
Version: 33554433
Fragment type: HashMapPartition
K Value: 6
Min load factor: 78
Max load factor: 80
Temporary table: no
Number of attributes: 4
Number of primary keys: 1
Length of frm data: 317
Max Rows: 0
Row Checksum: 1
Row GCI: 1
SingleUserMode: 0
ForceVarPart: 1
PartitionCount: 4
FragmentCount: 4
PartitionBalance: FOR_RP_BY_LDM
ExtraRowGciBits: 0
ExtraRowAuthorBits: 0
TableStatus: Retrieved
Table options:
HashMap: DEFAULT-HASHMAP-3840-4
-- Attributes --
c1 Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
c2 Int NULL AT=FIXED ST=MEMORY
c3 Int NULL AT=FIXED ST=MEMORY
c4 Int NULL AT=FIXED ST=DISK
-- Indexes --
PRIMARY KEY(c1) - UniqueHashIndex
i2(c3) - OrderedIndex
PRIMARY(c1) - OrderedIndex
i1(c2) - OrderedIndex

NDBT_ProgramExit: 0 - OK

Performance note.  The performance of a cluster using Disk Data storage is greatly improved if Disk Data files are kept on a separate physical disk from the data node file system. This must be done for each data node in the cluster to derive any noticeable benefit.

You can use absolute and relative file system paths with ADD UNDOFILE and ADD DATAFILE; relative paths are calculated with respect to the data node's data directory.

A log file group, a tablespace, and any Disk Data tables using these must be created in a particular order. This is also true for dropping these objects, sibject to the following constraints:

  • A log file group cannot be dropped as long as any tablespaces use it.

  • A tablespace cannot be dropped as long as it contains any data files.

  • You cannot drop any data files from a tablespace as long as there remain any tables which are using the tablespace.

  • It is not possible to drop files created in association with a different tablespace other than the one with which the files were created.

For example, to drop all the objects created so far in this section, you can use the following statements:

mysql> DROP TABLE dt_1;

mysql> ALTER TABLESPACE ts_1
    -> DROP DATAFILE 'data_2.dat'
    -> ENGINE NDBCLUSTER;

mysql> ALTER TABLESPACE ts_1
    -> DROP DATAFILE 'data_1.dat'
    -> ENGINE NDBCLUSTER;

mysql> DROP TABLESPACE ts_1
    -> ENGINE NDBCLUSTER;

mysql> DROP LOGFILE GROUP lg_1
    -> ENGINE NDBCLUSTER;

These statements must be performed in the order shown, except that the two ALTER TABLESPACE ... DROP DATAFILE statements may be executed in either order.

23.5.10.2 NDB Cluster Disk Data Storage Requirements

The following items apply to Disk Data storage requirements:

  • Variable-length columns of Disk Data tables take up a fixed amount of space. For each row, this is equal to the space required to store the largest possible value for that column.

    For general information about calculating these values, see Section 11.7, “Data Type Storage Requirements”.

    You can obtain an estimate the amount of space available in data files and undo log files by querying the INFORMATION_SCHEMA.FILES table. For more information and examples, see Section 26.15, “The INFORMATION_SCHEMA FILES Table”.

    Note

    The OPTIMIZE TABLE statement does not have any effect on Disk Data tables.

  • In a Disk Data table, the first 256 bytes of a TEXT or BLOB column are stored in memory; only the remainder is stored on disk.

  • Each row in a Disk Data table uses 8 bytes in memory to point to the data stored on disk. This means that, in some cases, converting an in-memory column to the disk-based format can actually result in greater memory usage. For example, converting a CHAR(4) column from memory-based to disk-based format increases the amount of DataMemory used per row from 4 to 8 bytes.

Important

Starting the cluster with the --initial option does not remove Disk Data files. You must remove these manually prior to performing an initial restart of the cluster.

Performance of Disk Data tables can be improved by minimizing the number of disk seeks by making sure that DiskPageBufferMemory is of sufficient size. You can query the diskpagebuffer table to help determine whether the value for this parameter needs to be increased.

23.5.11 Online Operations with ALTER TABLE in NDB Cluster

MySQL NDB Cluster 8.0 supports online table schema changes using the standard ALTER TABLE syntax employed by the MySQL Server (ALGORITHM=DEFAULT|INPLACE|COPY), and described elsewhere.

Note

Some older releases of NDB Cluster used a syntax specific to NDB for online ALTER TABLE operations. That syntax has since been removed.

Operations that add and drop indexes on variable-width columns of NDB tables occur online. Online operations are noncopying; that is, they do not require that indexes be re-created. They do not lock the table being altered from access by other API nodes in an NDB Cluster (but see Limitations of NDB online operations, later in this section). Such operations do not require single user mode for NDB table alterations made in an NDB cluster with multiple API nodes; transactions can continue uninterrupted during online DDL operations.

ALGORITHM=INPLACE can be used to perform online ADD COLUMN, ADD INDEX (including CREATE INDEX statements), and DROP INDEX operations on NDB tables. Online renaming of NDB tables is also supported.

Previously, columns of NDB tables could not be renamed online; this limitation is removed in NDB 8.0.18.

Currently you cannot add disk-based columns to NDB tables online. This means that, if you wish to add an in-memory column to an NDB table that uses a table-level STORAGE DISK option, you must declare the new column as using memory-based storage explicitly. For example—assuming that you have already created tablespace ts1—suppose that you create table t1 as follows:

mysql> CREATE TABLE t1 (
     >     c1 INT NOT NULL PRIMARY KEY,
     >     c2 VARCHAR(30)
     >     )
     >     TABLESPACE ts1 STORAGE DISK
     >     ENGINE NDB;
Query OK, 0 rows affected (1.73 sec)
Records: 0  Duplicates: 0  Warnings: 0

You can add a new in-memory column to this table online as shown here:

mysql> ALTER TABLE t1
     >     ADD COLUMN c3 INT COLUMN_FORMAT DYNAMIC STORAGE MEMORY,
     >     ALGORITHM=INPLACE;
Query OK, 0 rows affected (1.25 sec)
Records: 0  Duplicates: 0  Warnings: 0

This statement fails if the STORAGE MEMORY option is omitted:

mysql> ALTER TABLE t1
     >     ADD COLUMN c4 INT COLUMN_FORMAT DYNAMIC,
     >     ALGORITHM=INPLACE;
ERROR 1846 (0A000): ALGORITHM=INPLACE is not supported. Reason:
Adding column(s) or add/reorganize partition not supported online. Try
ALGORITHM=COPY.

If you omit the COLUMN_FORMAT DYNAMIC option, the dynamic column format is employed automatically, but a warning is issued, as shown here:

mysql> ALTER ONLINE TABLE t1 ADD COLUMN c4 INT STORAGE MEMORY;
Query OK, 0 rows affected, 1 warning (1.17 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW WARNINGS\G
*************************** 1. row ***************************
  Level: Warning
   Code: 1478
Message: DYNAMIC column c4 with STORAGE DISK is not supported, column will
become FIXED


mysql> SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `c1` int(11) NOT NULL,
  `c2` varchar(30) DEFAULT NULL,
  `c3` int(11) /*!50606 STORAGE MEMORY */ /*!50606 COLUMN_FORMAT DYNAMIC */ DEFAULT NULL,
  `c4` int(11) /*!50606 STORAGE MEMORY */ DEFAULT NULL,
  PRIMARY KEY (`c1`)
) /*!50606 TABLESPACE ts_1 STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=latin1
1 row in set (0.03 sec)
Note

The STORAGE and COLUMN_FORMAT keywords are supported only in NDB Cluster; in any other version of MySQL, attempting to use either of these keywords in a CREATE TABLE or ALTER TABLE statement results in an error.

It is also possible to use the statement ALTER TABLE ... REORGANIZE PARTITION, ALGORITHM=INPLACE with no partition_names INTO (partition_definitions) option on NDB tables. This can be used to redistribute NDB Cluster data among new data nodes that have been added to the cluster online. This does not perform any defragmentation, which requires an OPTIMIZE TABLE or null ALTER TABLE statement. For more information, see Section 23.5.7, “Adding NDB Cluster Data Nodes Online”.

Limitations of NDB online operations

Online DROP COLUMN operations are not supported.

Online ALTER TABLE, CREATE INDEX, or DROP INDEX statements that add columns or add or drop indexes are subject to the following limitations:

  • A given online ALTER TABLE can use only one of ADD COLUMN, ADD INDEX, or DROP INDEX. One or more columns can be added online in a single statement; only one index may be created or dropped online in a single statement.

  • The table being altered is not locked with respect to API nodes other than the one on which an online ALTER TABLE ADD COLUMN, ADD INDEX, or DROP INDEX operation (or CREATE INDEX or DROP INDEX statement) is run. However, the table is locked against any other operations originating on the same API node while the online operation is being executed.

  • The table to be altered must have an explicit primary key; the hidden primary key created by the NDB storage engine is not sufficient for this purpose.

  • The storage engine used by the table cannot be changed online.

  • The tablespace used by the table cannot be changed online. Beginning with NDB 8.0.21, a statement such as ALTER TABLE ndb_table ... ALGORITHM=INPLACE, TABLESPACE=new_tablespace is specifically disallowed. (Bug #99269, Bug #31180526)

  • When used with NDB Cluster Disk Data tables, it is not possible to change the storage type (DISK or MEMORY) of a column online. This means, that when you add or drop an index in such a way that the operation would be performed online, and you want the storage type of the column or columns to be changed, you must use ALGORITHM=COPY in the statement that adds or drops the index.

Columns to be added online cannot use the BLOB or TEXT type, and must meet the following criteria:

  • The columns must be dynamic; that is, it must be possible to create them using COLUMN_FORMAT DYNAMIC. If you omit the COLUMN_FORMAT DYNAMIC option, the dynamic column format is employed automatically.

  • The columns must permit NULL values and not have any explicit default value other than NULL. Columns added online are automatically created as DEFAULT NULL, as can be seen here:

    mysql> CREATE TABLE t2 (
         >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY
         >     ) ENGINE=NDB;
    Query OK, 0 rows affected (1.44 sec)
    
    mysql> ALTER TABLE t2
         >     ADD COLUMN c2 INT,
         >     ADD COLUMN c3 INT,
         >     ALGORITHM=INPLACE;
    Query OK, 0 rows affected, 2 warnings (0.93 sec)
    
    mysql> SHOW CREATE TABLE t1\G
    *************************** 1. row ***************************
           Table: t1
    Create Table: CREATE TABLE `t2` (
      `c1` int(11) NOT NULL AUTO_INCREMENT,
      `c2` int(11) DEFAULT NULL,
      `c3` int(11) DEFAULT NULL,
      PRIMARY KEY (`c1`)
    ) ENGINE=ndbcluster DEFAULT CHARSET=latin1
    1 row in set (0.00 sec)
    
  • The columns must be added following any existing columns. If you attempt to add a column online before any existing columns or using the FIRST keyword, the statement fails with an error.

  • Existing table columns cannot be reordered online.

For online ALTER TABLE operations on NDB tables, fixed-format columns are converted to dynamic when they are added online, or when indexes are created or dropped online, as shown here (repeating the CREATE TABLE and ALTER TABLE statements just shown for the sake of clarity):

mysql> CREATE TABLE t2 (
     >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY
     >     ) ENGINE=NDB;
Query OK, 0 rows affected (1.44 sec)

mysql> ALTER TABLE t2
     >     ADD COLUMN c2 INT,
     >     ADD COLUMN c3 INT,
     >     ALGORITHM=INPLACE;
Query OK, 0 rows affected, 2 warnings (0.93 sec)

mysql> SHOW WARNINGS;
*************************** 1. row ***************************
  Level: Warning
   Code: 1478
Message: Converted FIXED field 'c2' to DYNAMIC to enable online ADD COLUMN
*************************** 2. row ***************************
  Level: Warning
   Code: 1478
Message: Converted FIXED field 'c3' to DYNAMIC to enable online ADD COLUMN
2 rows in set (0.00 sec)

Only the column or columns to be added online must be dynamic. Existing columns need not be; this includes the table's primary key, which may also be FIXED, as shown here:

mysql> CREATE TABLE t3 (
     >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY COLUMN_FORMAT FIXED
     >     ) ENGINE=NDB;
Query OK, 0 rows affected (2.10 sec)

mysql> ALTER TABLE t3 ADD COLUMN c2 INT, ALGORITHM=INPLACE;
Query OK, 0 rows affected, 1 warning (0.78 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW WARNINGS;
*************************** 1. row ***************************
  Level: Warning
   Code: 1478
Message: Converted FIXED field 'c2' to DYNAMIC to enable online ADD COLUMN
1 row in set (0.00 sec)

Columns are not converted from FIXED to DYNAMIC column format by renaming operations. For more information about COLUMN_FORMAT, see Section 13.1.20, “CREATE TABLE Statement”.

The KEY, CONSTRAINT, and IGNORE keywords are supported in ALTER TABLE statements using ALGORITHM=INPLACE.

Setting MAX_ROWS to 0 using an online ALTER TABLE statement is disallowed. You must use a copying ALTER TABLE to perform this operation. (Bug #21960004)

23.5.12 Distributed MySQL Privileges with NDB_STORED_USER

NDB 8.0.18 introduces a new mechanism for sharing and synchronizing users, roles, and privileges between SQL nodes connected to an NDB Cluster. This can be enabled by granting the NDB_STORED_USER privilege. See the description of the privilege for usage information.

NDB_STORED_USER is printed in the output of SHOW GRANTS as with any other privilege. To verify that privileges are shared, use the ndb_select_all utility supplied with the NDB Cluster distribution, as shown here (some output wrapped to preserve formatting):

shell> ndb_select_all -d mysql ndb_sql_metadata
type    name    seq     note    sql_ddl_text
11      "'jon'@'localhost'"     0       4       "CREATE USER 'jon'@'localhost'
IDENTIFIED WITH 'caching_sha2_password' AS
'$A$005${B];3!?tI\".EFy\ZA5K5DQHrWiBvuRNYTIMeO0YeBlPpZotFRPjVTYzTA5b0' REQUIRE
NONE PASSWORD EXPIRE DEFAULT ACCOUNT UNLOCK PASSWORD HISTORY DEFAULT PASSWORD
REUSE INTERVAL DEFAULT PASSWORD REQUIRE CURRENT DEFAULT"
12      "'jon'@'localhost'"     0       [NULL]  "GRANT USAGE ON *.* TO `jon`@`localhost`"
12      "'jon'@'localhost'"     3       [NULL]  "GRANT ALL PRIVILEGES ON `test`.* TO `jon`@`localhost`"
12      "'jon'@'localhost'"     2       [NULL]  "GRANT ALL PRIVILEGES ON `mydb`.* TO `jon`@`localhost`"
12      "'jon'@'localhost'"     1       [NULL]  "GRANT NDB_STORED_USER ON *.* TO `jon`@`localhost`"
5 rows returned

ndb_sql_metadata is a special NDB table that is not visible using the mysql or other MySQL client.

A statement granting the NDB_STORED_USER privilege, such as GRANT NDB_STORED_USER ON *.* TO 'cluster_app_user'@'localhost', works by directing NDB to create a snapshot using the queries SHOW CREATE USER cluster_app_user@localhost and SHOW GRANTS FOR cluster_app_user@localhost, then storing the results in ndb_sql_metadata. Any other SQL nodes are then requested to read and apply the snapshot. Whenever a MySQL server starts up and joins the cluster as an SQL node it executes these stored CREATE USER and GRANT statements as part of the cluster schema synchronization process.

Whenever an SQL statement is executed on an SQL node other than the one where it originated, the statement is run in a utility thread of the NDBCLUSTER storage engine; this is done within a security environment equivalent to that of the MySQL replication replica applier thread.

You should be aware that changes to users with NDB_STORED_USER are distributed asynchronously. Because distributed schema change operations are performed synchronously, the next distributed schema change following a change to any distributed user or users serves as a synchronization point. Any pending user changes run to completion before the schema change distribution can begin; after this the schema change itself runs synchronously. For example, if a DROP DATABASE statement follows a DROP USER of a distributed user, the drop of the database cannot take place until the drop of the user has completed on all SQL nodes.

In the event that multiple GRANT, REVOKE, or other user administration statements from multiple SQL nodes cause privileges for a given user to diverge on different SQL nodes, you can fix this problem by issuing GRANT NDB_STORED_USER for this user on an SQL node where the privileges are known to be correct; this causes a new snapshot of the privileges to be taken and synchronized to the other SQL nodes.

NDB Cluster 8.0 does not support distribution of MySQL users and privileges across SQL nodes in an NDB Cluster by converting the MySQL privilege tables to use the NDB storage engine, as implemented in NDB 7.6 and earlier releases (see Distributed Privileges Using Shared Grant Tables). For information about the impact of this change on upgrades to NDB 8.0 from a previous release, see Section 23.2.7, “Upgrading and Downgrading NDB Cluster”.

23.5.13 NDB API Statistics Counters and Variables

A number of types of statistical counters relating to actions performed by or affecting Ndb objects are available. Such actions include starting and closing (or aborting) transactions; primary key and unique key operations; table, range, and pruned scans; threads blocked while waiting for the completion of various operations; and data and events sent and received by NDBCLUSTER. The counters are incremented inside the NDB kernel whenever NDB API calls are made or data is sent to or received by the data nodes. mysqld exposes these counters as system status variables; their values can be read in the output of SHOW STATUS, or by querying the Performance Schema session_status or global_status table. By comparing the values before and after statements operating on NDB tables, you can observe the corresponding actions taken on the API level, and thus the cost of performing the statement.

You can list all of these status variables using the following SHOW STATUS statement:

mysql> SHOW STATUS LIKE 'ndb_api%';
+--------------------------------------------+----------+
| Variable_name                              | Value    |
+--------------------------------------------+----------+
| Ndb_api_wait_exec_complete_count_session   | 0        |
| Ndb_api_wait_scan_result_count_session     | 0        |
| Ndb_api_wait_meta_request_count_session    | 0        |
| Ndb_api_wait_nanos_count_session           | 0        |
| Ndb_api_bytes_sent_count_session           | 0        |
| Ndb_api_bytes_received_count_session       | 0        |
| Ndb_api_trans_start_count_session          | 0        |
| Ndb_api_trans_commit_count_session         | 0        |
| Ndb_api_trans_abort_count_session          | 0        |
| Ndb_api_trans_close_count_session          | 0        |
| Ndb_api_pk_op_count_session                | 0        |
| Ndb_api_uk_op_count_session                | 0        |
| Ndb_api_table_scan_count_session           | 0        |
| Ndb_api_range_scan_count_session           | 0        |
| Ndb_api_pruned_scan_count_session          | 0        |
| Ndb_api_scan_batch_count_session           | 0        |
| Ndb_api_read_row_count_session             | 0        |
| Ndb_api_trans_local_read_row_count_session | 0        |
| Ndb_api_event_data_count_injector          | 0        |
| Ndb_api_event_nondata_count_injector       | 0        |
| Ndb_api_event_bytes_count_injector         | 0        |
| Ndb_api_wait_exec_complete_count_slave     | 0        |
| Ndb_api_wait_scan_result_count_slave       | 0        |
| Ndb_api_wait_meta_request_count_slave      | 0        |
| Ndb_api_wait_nanos_count_slave             | 0        |
| Ndb_api_bytes_sent_count_slave             | 0        |
| Ndb_api_bytes_received_count_slave         | 0        |
| Ndb_api_trans_start_count_slave            | 0        |
| Ndb_api_trans_commit_count_slave           | 0        |
| Ndb_api_trans_abort_count_slave            | 0        |
| Ndb_api_trans_close_count_slave            | 0        |
| Ndb_api_pk_op_count_slave                  | 0        |
| Ndb_api_uk_op_count_slave                  | 0        |
| Ndb_api_table_scan_count_slave             | 0        |
| Ndb_api_range_scan_count_slave             | 0        |
| Ndb_api_pruned_scan_count_slave            | 0        |
| Ndb_api_scan_batch_count_slave             | 0        |
| Ndb_api_read_row_count_slave               | 0        |
| Ndb_api_trans_local_read_row_count_slave   | 0        |
| Ndb_api_wait_exec_complete_count           | 2        |
| Ndb_api_wait_scan_result_count             | 3        |
| Ndb_api_wait_meta_request_count            | 27       |
| Ndb_api_wait_nanos_count                   | 45612023 |
| Ndb_api_bytes_sent_count                   | 992      |
| Ndb_api_bytes_received_count               | 9640     |
| Ndb_api_trans_start_count                  | 2        |
| Ndb_api_trans_commit_count                 | 1        |
| Ndb_api_trans_abort_count                  | 0        |
| Ndb_api_trans_close_count                  | 2        |
| Ndb_api_pk_op_count                        | 1        |
| Ndb_api_uk_op_count                        | 0        |
| Ndb_api_table_scan_count                   | 1        |
| Ndb_api_range_scan_count                   | 0        |
| Ndb_api_pruned_scan_count                  | 0        |
| Ndb_api_scan_batch_count                   | 0        |
| Ndb_api_read_row_count                     | 1        |
| Ndb_api_trans_local_read_row_count         | 1        |
| Ndb_api_event_data_count                   | 0        |
| Ndb_api_event_nondata_count                | 0        |
| Ndb_api_event_bytes_count                  | 0        |
+--------------------------------------------+----------+
60 rows in set (0.02 sec)

These status variables are also available from the Performance Schema session_status and global_status tables, as shown here:

mysql> SELECT * FROM performance_schema.session_status
    ->   WHERE VARIABLE_NAME LIKE 'ndb_api%';
+--------------------------------------------+----------------+
| VARIABLE_NAME                              | VARIABLE_VALUE |
+--------------------------------------------+----------------+
| NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION   | 2              |
| NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION     | 0              |
| NDB_API_WAIT_META_REQUEST_COUNT_SESSION    | 1              |
| NDB_API_WAIT_NANOS_COUNT_SESSION           | 8144375        |
| NDB_API_BYTES_SENT_COUNT_SESSION           | 68             |
| NDB_API_BYTES_RECEIVED_COUNT_SESSION       | 84             |
| NDB_API_TRANS_START_COUNT_SESSION          | 1              |
| NDB_API_TRANS_COMMIT_COUNT_SESSION         | 1              |
| NDB_API_TRANS_ABORT_COUNT_SESSION          | 0              |
| NDB_API_TRANS_CLOSE_COUNT_SESSION          | 1              |
| NDB_API_PK_OP_COUNT_SESSION                | 1              |
| NDB_API_UK_OP_COUNT_SESSION                | 0              |
| NDB_API_TABLE_SCAN_COUNT_SESSION           | 0              |
| NDB_API_RANGE_SCAN_COUNT_SESSION           | 0              |
| NDB_API_PRUNED_SCAN_COUNT_SESSION          | 0              |
| NDB_API_SCAN_BATCH_COUNT_SESSION           | 0              |
| NDB_API_READ_ROW_COUNT_SESSION             | 1              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1              |
| NDB_API_EVENT_DATA_COUNT_INJECTOR          | 0              |
| NDB_API_EVENT_NONDATA_COUNT_INJECTOR       | 0              |
| NDB_API_EVENT_BYTES_COUNT_INJECTOR         | 0              |
| NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE     | 0              |
| NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE       | 0              |
| NDB_API_WAIT_META_REQUEST_COUNT_SLAVE      | 0              |
| NDB_API_WAIT_NANOS_COUNT_SLAVE             | 0              |
| NDB_API_BYTES_SENT_COUNT_SLAVE             | 0              |
| NDB_API_BYTES_RECEIVED_COUNT_SLAVE         | 0              |
| NDB_API_TRANS_START_COUNT_SLAVE            | 0              |
| NDB_API_TRANS_COMMIT_COUNT_SLAVE           | 0              |
| NDB_API_TRANS_ABORT_COUNT_SLAVE            | 0              |
| NDB_API_TRANS_CLOSE_COUNT_SLAVE            | 0              |
| NDB_API_PK_OP_COUNT_SLAVE                  | 0              |
| NDB_API_UK_OP_COUNT_SLAVE                  | 0              |
| NDB_API_TABLE_SCAN_COUNT_SLAVE             | 0              |
| NDB_API_RANGE_SCAN_COUNT_SLAVE             | 0              |
| NDB_API_PRUNED_SCAN_COUNT_SLAVE            | 0              |
| NDB_API_SCAN_BATCH_COUNT_SLAVE             | 0              |
| NDB_API_READ_ROW_COUNT_SLAVE               | 0              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE   | 0              |
| NDB_API_WAIT_EXEC_COMPLETE_COUNT           | 4              |
| NDB_API_WAIT_SCAN_RESULT_COUNT             | 3              |
| NDB_API_WAIT_META_REQUEST_COUNT            | 28             |
| NDB_API_WAIT_NANOS_COUNT                   | 53756398       |
| NDB_API_BYTES_SENT_COUNT                   | 1060           |
| NDB_API_BYTES_RECEIVED_COUNT               | 9724           |
| NDB_API_TRANS_START_COUNT                  | 3              |
| NDB_API_TRANS_COMMIT_COUNT                 | 2              |
| NDB_API_TRANS_ABORT_COUNT                  | 0              |
| NDB_API_TRANS_CLOSE_COUNT                  | 3              |
| NDB_API_PK_OP_COUNT                        | 2              |
| NDB_API_UK_OP_COUNT                        | 0              |
| NDB_API_TABLE_SCAN_COUNT                   | 1              |
| NDB_API_RANGE_SCAN_COUNT                   | 0              |
| NDB_API_PRUNED_SCAN_COUNT                  | 0              |
| NDB_API_SCAN_BATCH_COUNT                   | 0              |
| NDB_API_READ_ROW_COUNT                     | 2              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT         | 2              |
| NDB_API_EVENT_DATA_COUNT                   | 0              |
| NDB_API_EVENT_NONDATA_COUNT                | 0              |
| NDB_API_EVENT_BYTES_COUNT                  | 0              |
+--------------------------------------------+----------------+
60 rows in set (0.00 sec)

mysql> SELECT * FROM performance_schema.global_status
    ->     WHERE VARIABLE_NAME LIKE 'ndb_api%';
+--------------------------------------------+----------------+
| VARIABLE_NAME                              | VARIABLE_VALUE |
+--------------------------------------------+----------------+
| NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION   | 2              |
| NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION     | 0              |
| NDB_API_WAIT_META_REQUEST_COUNT_SESSION    | 1              |
| NDB_API_WAIT_NANOS_COUNT_SESSION           | 8144375        |
| NDB_API_BYTES_SENT_COUNT_SESSION           | 68             |
| NDB_API_BYTES_RECEIVED_COUNT_SESSION       | 84             |
| NDB_API_TRANS_START_COUNT_SESSION          | 1              |
| NDB_API_TRANS_COMMIT_COUNT_SESSION         | 1              |
| NDB_API_TRANS_ABORT_COUNT_SESSION          | 0              |
| NDB_API_TRANS_CLOSE_COUNT_SESSION          | 1              |
| NDB_API_PK_OP_COUNT_SESSION                | 1              |
| NDB_API_UK_OP_COUNT_SESSION                | 0              |
| NDB_API_TABLE_SCAN_COUNT_SESSION           | 0              |
| NDB_API_RANGE_SCAN_COUNT_SESSION           | 0              |
| NDB_API_PRUNED_SCAN_COUNT_SESSION          | 0              |
| NDB_API_SCAN_BATCH_COUNT_SESSION           | 0              |
| NDB_API_READ_ROW_COUNT_SESSION             | 1              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1              |
| NDB_API_EVENT_DATA_COUNT_INJECTOR          | 0              |
| NDB_API_EVENT_NONDATA_COUNT_INJECTOR       | 0              |
| NDB_API_EVENT_BYTES_COUNT_INJECTOR         | 0              |
| NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE     | 0              |
| NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE       | 0              |
| NDB_API_WAIT_META_REQUEST_COUNT_SLAVE      | 0              |
| NDB_API_WAIT_NANOS_COUNT_SLAVE             | 0              |
| NDB_API_BYTES_SENT_COUNT_SLAVE             | 0              |
| NDB_API_BYTES_RECEIVED_COUNT_SLAVE         | 0              |
| NDB_API_TRANS_START_COUNT_SLAVE            | 0              |
| NDB_API_TRANS_COMMIT_COUNT_SLAVE           | 0              |
| NDB_API_TRANS_ABORT_COUNT_SLAVE            | 0              |
| NDB_API_TRANS_CLOSE_COUNT_SLAVE            | 0              |
| NDB_API_PK_OP_COUNT_SLAVE                  | 0              |
| NDB_API_UK_OP_COUNT_SLAVE                  | 0              |
| NDB_API_TABLE_SCAN_COUNT_SLAVE             | 0              |
| NDB_API_RANGE_SCAN_COUNT_SLAVE             | 0              |
| NDB_API_PRUNED_SCAN_COUNT_SLAVE            | 0              |
| NDB_API_SCAN_BATCH_COUNT_SLAVE             | 0              |
| NDB_API_READ_ROW_COUNT_SLAVE               | 0              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE   | 0              |
| NDB_API_WAIT_EXEC_COMPLETE_COUNT           | 4              |
| NDB_API_WAIT_SCAN_RESULT_COUNT             | 3              |
| NDB_API_WAIT_META_REQUEST_COUNT            | 28             |
| NDB_API_WAIT_NANOS_COUNT                   | 53756398       |
| NDB_API_BYTES_SENT_COUNT                   | 1060           |
| NDB_API_BYTES_RECEIVED_COUNT               | 9724           |
| NDB_API_TRANS_START_COUNT                  | 3              |
| NDB_API_TRANS_COMMIT_COUNT                 | 2              |
| NDB_API_TRANS_ABORT_COUNT                  | 0              |
| NDB_API_TRANS_CLOSE_COUNT                  | 3              |
| NDB_API_PK_OP_COUNT                        | 2              |
| NDB_API_UK_OP_COUNT                        | 0              |
| NDB_API_TABLE_SCAN_COUNT                   | 1              |
| NDB_API_RANGE_SCAN_COUNT                   | 0              |
| NDB_API_PRUNED_SCAN_COUNT                  | 0              |
| NDB_API_SCAN_BATCH_COUNT                   | 0              |
| NDB_API_READ_ROW_COUNT                     | 2              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT         | 2              |
| NDB_API_EVENT_DATA_COUNT                   | 0              |
| NDB_API_EVENT_NONDATA_COUNT                | 0              |
| NDB_API_EVENT_BYTES_COUNT                  | 0              |
+--------------------------------------------+----------------+
60 rows in set (0.00 sec)

Each Ndb object has its own counters. NDB API applications can read the values of the counters for use in optimization or monitoring. For multithreaded clients which use more than one Ndb object concurrently, it is also possible to obtain a summed view of counters from all Ndb objects belonging to a given Ndb_cluster_connection.

Four sets of these counters are exposed. One set applies to the current session only; the other 3 are global. This is in spite of the fact that their values can be obtained as either session or global status variables in the mysql client. This means that specifying the SESSION or GLOBAL keyword with SHOW STATUS has no effect on the values reported for NDB API statistics status variables, and the value for each of these variables is the same whether the value is obtained from the equivalent column of the session_status or the global_status table.

  • Session counters (session specific)

    Session counters relate to the Ndb objects in use by (only) the current session. Use of such objects by other MySQL clients does not influence these counts.

    In order to minimize confusion with standard MySQL session variables, we refer to the variables that correspond to these NDB API session counters as _session variables, with a leading underscore.

  • Replica counters (global)

    This set of counters relates to the Ndb objects used by the replica SQL thread, if any. If this mysqld does not act as a replica, or does not use NDB tables, then all of these counts are 0.

    We refer to the related status variables as _slave variables (with a leading underscore).

  • Injector counters (global)

    Injector counters relate to the Ndb object used to listen to cluster events by the binary log injector thread. Even when not writing a binary log, mysqld processes attached to an NDB Cluster continue to listen for some events, such as schema changes.

    We refer to the status variables that correspond to NDB API injector counters as _injector variables (with a leading underscore).

  • Server (Global) counters (global)

    This set of counters relates to all Ndb objects currently used by this mysqld. This includes all MySQL client applications, the replica SQL thread (if any), the binary log injector, and the NDB utility thread.

    We refer to the status variables that correspond to these counters as global variables or mysqld-level variables.

You can obtain values for a particular set of variables by additionally filtering for the substring session, slave, or injector in the variable name (along with the common prefix Ndb_api). For _session variables, this can be done as shown here:

mysql> SHOW STATUS LIKE 'ndb_api%session';
+--------------------------------------------+---------+
| Variable_name                              | Value   |
+--------------------------------------------+---------+
| Ndb_api_wait_exec_complete_count_session   | 2       |
| Ndb_api_wait_scan_result_count_session     | 0       |
| Ndb_api_wait_meta_request_count_session    | 1       |
| Ndb_api_wait_nanos_count_session           | 8144375 |
| Ndb_api_bytes_sent_count_session           | 68      |
| Ndb_api_bytes_received_count_session       | 84      |
| Ndb_api_trans_start_count_session          | 1       |
| Ndb_api_trans_commit_count_session         | 1       |
| Ndb_api_trans_abort_count_session          | 0       |
| Ndb_api_trans_close_count_session          | 1       |
| Ndb_api_pk_op_count_session                | 1       |
| Ndb_api_uk_op_count_session                | 0       |
| Ndb_api_table_scan_count_session           | 0       |
| Ndb_api_range_scan_count_session           | 0       |
| Ndb_api_pruned_scan_count_session          | 0       |
| Ndb_api_scan_batch_count_session           | 0       |
| Ndb_api_read_row_count_session             | 1       |
| Ndb_api_trans_local_read_row_count_session | 1       |
+--------------------------------------------+---------+
18 rows in set (0.50 sec)

To obtain a listing of the NDB API mysqld-level status variables, filter for variable names beginning with ndb_api and ending in _count, like this:

mysql> SELECT * FROM performance_schema.session_status
    ->     WHERE VARIABLE_NAME LIKE 'ndb_api%count';
+------------------------------------+----------------+
| VARIABLE_NAME                      | VARIABLE_VALUE |
+------------------------------------+----------------+
| NDB_API_WAIT_EXEC_COMPLETE_COUNT   | 4              |
| NDB_API_WAIT_SCAN_RESULT_COUNT     | 3              |
| NDB_API_WAIT_META_REQUEST_COUNT    | 28             |
| NDB_API_WAIT_NANOS_COUNT           | 53756398       |
| NDB_API_BYTES_SENT_COUNT           | 1060           |
| NDB_API_BYTES_RECEIVED_COUNT       | 9724           |
| NDB_API_TRANS_START_COUNT          | 3              |
| NDB_API_TRANS_COMMIT_COUNT         | 2              |
| NDB_API_TRANS_ABORT_COUNT          | 0              |
| NDB_API_TRANS_CLOSE_COUNT          | 3              |
| NDB_API_PK_OP_COUNT                | 2              |
| NDB_API_UK_OP_COUNT                | 0              |
| NDB_API_TABLE_SCAN_COUNT           | 1              |
| NDB_API_RANGE_SCAN_COUNT           | 0              |
| NDB_API_PRUNED_SCAN_COUNT          | 0              |
| NDB_API_SCAN_BATCH_COUNT           | 0              |
| NDB_API_READ_ROW_COUNT             | 2              |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2              |
| NDB_API_EVENT_DATA_COUNT           | 0              |
| NDB_API_EVENT_NONDATA_COUNT        | 0              |
| NDB_API_EVENT_BYTES_COUNT          | 0              |
+------------------------------------+----------------+
21 rows in set (0.09 sec)

Not all counters are reflected in all 4 sets of status variables. For the event counters DataEventsRecvdCount, NondataEventsRecvdCount, and EventBytesRecvdCount, only _injector and mysqld-level NDB API status variables are available:

mysql> SHOW STATUS LIKE 'ndb_api%event%';
+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector    | 0     |
| Ndb_api_event_nondata_count_injector | 0     |
| Ndb_api_event_bytes_count_injector   | 0     |
| Ndb_api_event_data_count             | 0     |
| Ndb_api_event_nondata_count          | 0     |
| Ndb_api_event_bytes_count            | 0     |
+--------------------------------------+-------+
6 rows in set (0.00 sec)

_injector status variables are not implemented for any other NDB API counters, as shown here:

mysql> SHOW STATUS LIKE 'ndb_api%injector%';
+--------------------------------------+-------+
| Variable_name                        | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector    | 0     |
| Ndb_api_event_nondata_count_injector | 0     |
| Ndb_api_event_bytes_count_injector   | 0     |
+--------------------------------------+-------+
3 rows in set (0.00 sec)

The names of the status variables can easily be associated with the names of the corresponding counters. Each NDB API statistics counter is listed in the following table with a description as well as the names of any MySQL server status variables corresponding to this counter.

Table 23.66 NDB API statistics counters

Counter Name Description Status Variables (by statistic type):
  • Session

  • Slave (replica)

  • Injector

  • Server

WaitExecCompleteCount Number of times thread has been blocked while waiting for execution of an operation to complete. Includes all execute() calls as well as implicit executes for blob operations and auto-increment not visible to clients.
WaitScanResultCount Number of times thread has been blocked while waiting for a scan-based signal, such waiting for additional results, or for a scan to close.
WaitMetaRequestCount Number of times thread has been blocked waiting for a metadata-based signal; this can occur when waiting for a DDL operation or for an epoch to be started (or ended).
WaitNanosCount Total time (in nanoseconds) spent waiting for some type of signal from the data nodes.
BytesSentCount Amount of data (in bytes) sent to the data nodes
BytesRecvdCount Amount of data (in bytes) received from the data nodes
TransStartCount Number of transactions started.
TransCommitCount Number of transactions committed.
TransAbortCount Number of transactions aborted.
TransCloseCount Number of transactions aborted. (This value may be greater than the sum of TransCommitCount and TransAbortCount.)
PkOpCount Number of operations based on or using primary keys. This count includes blob-part table operations, implicit unlocking operations, and auto-increment operations, as well as primary key operations normally visible to MySQL clients.
UkOpCount Number of operations based on or using unique keys.
TableScanCount Number of table scans that have been started. This includes scans of internal tables.
RangeScanCount Number of range scans that have been started.
PrunedScanCount Number of scans that have been pruned to a single partition.
ScanBatchCount Number of batches of rows received. (A batch in this context is a set of scan results from a single fragment.)
ReadRowCount Total number of rows that have been read. Includes rows read using primary key, unique key, and scan operations.
TransLocalReadRowCount Number of rows read from the data same node on which the transaction was being run.
DataEventsRecvdCount Number of row change events received.
NondataEventsRecvdCount Number of events received, other than row change events.
EventBytesRecvdCount Number of bytes of events received.

To see all counts of committed transactions—that is, all TransCommitCount counter status variables—you can filter the results of SHOW STATUS for the substring trans_commit_count, like this:

mysql> SHOW STATUS LIKE '%trans_commit_count%';
+------------------------------------+-------+
| Variable_name                      | Value |
+------------------------------------+-------+
| Ndb_api_trans_commit_count_session | 1     |
| Ndb_api_trans_commit_count_slave   | 0     |
| Ndb_api_trans_commit_count         | 2     |
+------------------------------------+-------+
3 rows in set (0.00 sec)

From this you can determine that 1 transaction has been committed in the current mysql client session, and 2 transactions have been committed on this mysqld since it was last restarted.

You can see how various NDB API counters are incremented by a given SQL statement by comparing the values of the corresponding _session status variables immediately before and after performing the statement. In this example, after getting the initial values from SHOW STATUS, we create in the test database an NDB table, named t, that has a single column:

mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+--------+
| Variable_name                              | Value  |
+--------------------------------------------+--------+
| Ndb_api_wait_exec_complete_count_session   | 2      |
| Ndb_api_wait_scan_result_count_session     | 0      |
| Ndb_api_wait_meta_request_count_session    | 3      |
| Ndb_api_wait_nanos_count_session           | 820705 |
| Ndb_api_bytes_sent_count_session           | 132    |
| Ndb_api_bytes_received_count_session       | 372    |
| Ndb_api_trans_start_count_session          | 1      |
| Ndb_api_trans_commit_count_session         | 1      |
| Ndb_api_trans_abort_count_session          | 0      |
| Ndb_api_trans_close_count_session          | 1      |
| Ndb_api_pk_op_count_session                | 1      |
| Ndb_api_uk_op_count_session                | 0      |
| Ndb_api_table_scan_count_session           | 0      |
| Ndb_api_range_scan_count_session           | 0      |
| Ndb_api_pruned_scan_count_session          | 0      |
| Ndb_api_scan_batch_count_session           | 0      |
| Ndb_api_read_row_count_session             | 1      |
| Ndb_api_trans_local_read_row_count_session | 1      |
+--------------------------------------------+--------+
18 rows in set (0.00 sec)

mysql> USE test;
Database changed
mysql> CREATE TABLE t (c INT) ENGINE NDBCLUSTER;
Query OK, 0 rows affected (0.85 sec)

Now you can execute a new SHOW STATUS statement and observe the changes, as shown here (with the changed rows highlighted in the output):

mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+-----------+
| Variable_name                              | Value     |
+--------------------------------------------+-----------+
| Ndb_api_wait_exec_complete_count_session   | 8         |
| Ndb_api_wait_scan_result_count_session     | 0         |
| Ndb_api_wait_meta_request_count_session    | 17        |
| Ndb_api_wait_nanos_count_session           | 706871709 |
| Ndb_api_bytes_sent_count_session           | 2376      |
| Ndb_api_bytes_received_count_session       | 3844      |
| Ndb_api_trans_start_count_session          | 4         |
| Ndb_api_trans_commit_count_session         | 4         |
| Ndb_api_trans_abort_count_session          | 0         |
| Ndb_api_trans_close_count_session          | 4         |
| Ndb_api_pk_op_count_session                | 6         |
| Ndb_api_uk_op_count_session                | 0         |
| Ndb_api_table_scan_count_session           | 0         |
| Ndb_api_range_scan_count_session           | 0         |
| Ndb_api_pruned_scan_count_session          | 0         |
| Ndb_api_scan_batch_count_session           | 0         |
| Ndb_api_read_row_count_session             | 2         |
| Ndb_api_trans_local_read_row_count_session | 1         |
+--------------------------------------------+-----------+
18 rows in set (0.00 sec)

Similarly, you can see the changes in the NDB API statistics counters caused by inserting a row into t: Insert the row, then run the same SHOW STATUS statement used in the previous example, as shown here:

mysql> INSERT INTO t VALUES (100);
Query OK, 1 row affected (0.00 sec)

mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+-----------+
| Variable_name                              | Value     |
+--------------------------------------------+-----------+
| Ndb_api_wait_exec_complete_count_session   | 11        |
| Ndb_api_wait_scan_result_count_session     | 6         |
| Ndb_api_wait_meta_request_count_session    | 20        |
| Ndb_api_wait_nanos_count_session           | 707370418 |
| Ndb_api_bytes_sent_count_session           | 2724      |
| Ndb_api_bytes_received_count_session       | 4116      |
| Ndb_api_trans_start_count_session          | 7         |
| Ndb_api_trans_commit_count_session         | 6         |
| Ndb_api_trans_abort_count_session          | 0         |
| Ndb_api_trans_close_count_session          | 7         |
| Ndb_api_pk_op_count_session                | 8         |
| Ndb_api_uk_op_count_session                | 0         |
| Ndb_api_table_scan_count_session           | 1         |
| Ndb_api_range_scan_count_session           | 0         |
| Ndb_api_pruned_scan_count_session          | 0         |
| Ndb_api_scan_batch_count_session           | 0         |
| Ndb_api_read_row_count_session             | 3         |
| Ndb_api_trans_local_read_row_count_session | 2         |
+--------------------------------------------+-----------+
18 rows in set (0.00 sec)

We can make a number of observations from these results:

  • Although we created t with no explicit primary key, 5 primary key operations were performed in doing so (the difference in the before and after values of Ndb_api_pk_op_count_session, or 6 minus 1). This reflects the creation of the hidden primary key that is a feature of all tables using the NDB storage engine.

  • By comparing successive values for Ndb_api_wait_nanos_count_session, we can see that the NDB API operations implementing the CREATE TABLE statement waited much longer (706871709 - 820705 = 706051004 nanoseconds, or approximately 0.7 second) for responses from the data nodes than those executed by the INSERT (707370418 - 706871709 = 498709 ns or roughly .0005 second). The execution times reported for these statements in the mysql client correlate roughly with these figures.

    On platforms without sufficient (nanosecond) time resolution, small changes in the value of the WaitNanosCount NDB API counter due to SQL statements that execute very quickly may not always be visible in the values of Ndb_api_wait_nanos_count_session, Ndb_api_wait_nanos_count_slave, or Ndb_api_wait_nanos_count.

  • The INSERT statement incremented both the ReadRowCount and TransLocalReadRowCount NDB API statistics counters, as reflected by the increased values of Ndb_api_read_row_count_session and Ndb_api_trans_local_read_row_count_session.

23.5.14 ndbinfo: The NDB Cluster Information Database

23.5.14.1 The ndbinfo arbitrator_validity_detail Table
23.5.14.2 The ndbinfo arbitrator_validity_summary Table
23.5.14.3 The ndbinfo backup_id Table
23.5.14.4 The ndbinfo blocks Table
23.5.14.5 The ndbinfo cluster_locks Table
23.5.14.6 The ndbinfo cluster_operations Table
23.5.14.7 The ndbinfo cluster_transactions Table
23.5.14.8 The ndbinfo config_nodes Table
23.5.14.9 The ndbinfo config_params Table
23.5.14.10 The ndbinfo config_values Table
23.5.14.11 The ndbinfo counters Table
23.5.14.12 The ndbinfo cpudata Table
23.5.14.13 The ndbinfo cpudata_1sec Table
23.5.14.14 The ndbinfo cpudata_20sec Table
23.5.14.15 The ndbinfo cpudata_50ms Table
23.5.14.16 The ndbinfo cpuinfo Table
23.5.14.17 The ndbinfo cpustat Table
23.5.14.18 The ndbinfo cpustat_50ms Table
23.5.14.19 The ndbinfo cpustat_1sec Table
23.5.14.20 The ndbinfo cpustat_20sec Table
23.5.14.21 The ndbinfo dict_obj_info Table
23.5.14.22 The ndbinfo dict_obj_tree Table
23.5.14.23 The ndbinfo dict_obj_types Table
23.5.14.24 The ndbinfo disk_write_speed_base Table
23.5.14.25 The ndbinfo disk_write_speed_aggregate Table
23.5.14.26 The ndbinfo disk_write_speed_aggregate_node Table
23.5.14.27 The ndbinfo diskpagebuffer Table
23.5.14.28 The ndbinfo diskstat Table
23.5.14.29 The ndbinfo diskstats_1sec Table
23.5.14.30 The ndbinfo error_messages Table
23.5.14.31 The ndbinfo hwinfo Table
23.5.14.32 The ndbinfo locks_per_fragment Table
23.5.14.33 The ndbinfo logbuffers Table
23.5.14.34 The ndbinfo logspaces Table
23.5.14.35 The ndbinfo membership Table
23.5.14.36 The ndbinfo memoryusage Table
23.5.14.37 The ndbinfo memory_per_fragment Table
23.5.14.38 The ndbinfo nodes Table
23.5.14.39 The ndbinfo operations_per_fragment Table
23.5.14.40 The ndbinfo pgman_time_track_stats Table
23.5.14.41 The ndbinfo processes Table
23.5.14.42 The ndbinfo resources Table
23.5.14.43 The ndbinfo restart_info Table
23.5.14.44 The ndbinfo server_locks Table
23.5.14.45 The ndbinfo server_operations Table
23.5.14.46 The ndbinfo server_transactions Table
23.5.14.47 The ndbinfo table_distribution_status Table
23.5.14.48 The ndbinfo table_fragments Table
23.5.14.49 The ndbinfo table_info Table
23.5.14.50 The ndbinfo table_replicas Table
23.5.14.51 The ndbinfo tc_time_track_stats Table
23.5.14.52 The ndbinfo threadblocks Table
23.5.14.53 The ndbinfo threads Table
23.5.14.54 The ndbinfo threadstat Table
23.5.14.55 The ndbinfo transporters Table

ndbinfo is a database containing information specific to NDB Cluster.

This database contains a number of tables, each providing a different sort of data about NDB Cluster node status, resource usage, and operations. You can find more detailed information about each of these tables in the next several sections.

ndbinfo is included with NDB Cluster support in the MySQL Server; no special compilation or configuration steps are required; the tables are created by the MySQL Server when it connects to the cluster. You can verify that ndbinfo support is active in a given MySQL Server instance using SHOW PLUGINS; if ndbinfo support is enabled, you should see a row containing ndbinfo in the Name column and ACTIVE in the Status column, as shown here (emphasized text):

mysql> SHOW PLUGINS;
+----------------------------------+--------+--------------------+---------+---------+
| Name                             | Status | Type               | Library | License |
+----------------------------------+--------+--------------------+---------+---------+
| binlog                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| mysql_native_password            | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| sha256_password                  | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| MRG_MYISAM                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MEMORY                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| CSV                              | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MyISAM                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| InnoDB                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| INNODB_TRX                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_LOCKS                     | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_LOCK_WAITS                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_RESET                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM                    | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM_RESET              | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_PER_INDEX             | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_PER_INDEX_RESET       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_PAGE               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_PAGE_LRU           | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_POOL_STATS         | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TEMP_TABLE_INFO           | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_METRICS                   | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_DEFAULT_STOPWORD       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_DELETED                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_BEING_DELETED          | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_CONFIG                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_INDEX_CACHE            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_INDEX_TABLE            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_TABLES                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_TABLESTATS            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_INDEXES               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_COLUMNS               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_FIELDS                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_FOREIGN               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_FOREIGN_COLS          | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_TABLESPACES           | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_DATAFILES             | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SYS_VIRTUAL               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| PERFORMANCE_SCHEMA               | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbCluster                      | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbinfo                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndb_transid_mysql_connection_map | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| BLACKHOLE                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ARCHIVE                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| partition                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ngram                            | ACTIVE | FTPARSER           | NULL    | GPL     |
+----------------------------------+--------+--------------------+---------+---------+
46 rows in set (0.00 sec)

You can also do this by checking the output of SHOW ENGINES for a line including ndbinfo in the Engine column and YES in the Support column, as shown here (emphasized text):

mysql> SHOW ENGINES\G
*************************** 1. row ***************************
      Engine: ndbcluster
     Support: YES
     Comment: Clustered, fault-tolerant tables
Transactions: YES
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 4. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 6. row ***************************
      Engine: MRG_MYISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: ndbinfo
     Support: YES
     Comment: NDB Cluster system information storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 10. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
10 rows in set (0.00 sec)

If ndbinfo support is enabled, then you can access ndbinfo using SQL statements in mysql or another MySQL client. For example, you can see ndbinfo listed in the output of SHOW DATABASES, as shown here (emphasized text):

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| ndbinfo            |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.04 sec)

If the mysqld process was not started with the --ndbcluster option, ndbinfo is not available and is not displayed by SHOW DATABASES. If mysqld was formerly connected to an NDB Cluster but the cluster becomes unavailable (due to events such as cluster shutdown, loss of network connectivity, and so forth), ndbinfo and its tables remain visible, but an attempt to access any tables (other than blocks or config_params) fails with Got error 157 'Connection to NDB failed' from NDBINFO.

With the exception of the blocks and config_params tables, what we refer to as ndbinfo tables are actually views generated from internal NDB tables not normally visible to the MySQL Server.

All ndbinfo tables are read-only, and are generated on demand when queried. Because many of them are generated in parallel by the data nodes while other are specific to a given SQL node, they are not guaranteed to provide a consistent snapshot.

In addition, pushing down of joins is not supported on ndbinfo tables; so joining large ndbinfo tables can require transfer of a large amount of data to the requesting API node, even when the query makes use of a WHERE clause.

ndbinfo tables are not included in the query cache. (Bug #59831)

You can select the ndbinfo database with a USE statement, and then issue a SHOW TABLES statement to obtain a list of tables, just as for any other database, like this:

mysql> USE ndbinfo;
Database changed

mysql> SHOW TABLES;
+---------------------------------+
| Tables_in_ndbinfo               |
+---------------------------------+
| arbitrator_validity_detail      |
| arbitrator_validity_summary     |
| blocks                          |
| cluster_locks                   |
| cluster_operations              |
| cluster_transactions            |
| config_nodes                    |
| config_params                   |
| config_values                   |
| counters                        |
| cpustat                         |
| cpustat_1sec                    |
| cpustat_20sec                   |
| cpustat_50ms                    |
| dict_obj_info                   |
| dict_obj_types                  |
| disk_write_speed_aggregate      |
| disk_write_speed_aggregate_node |
| disk_write_speed_base           |
| diskpagebuffer                  |
| error_messages                  |
| locks_per_fragment              |
| logbuffers                      |
| logspaces                       |
| membership                      |
| memory_per_fragment             |
| memoryusage                     |
| nodes                           |
| operations_per_fragment         |
| processes                       |
| resources                       |
| restart_info                    |
| server_locks                    |
| server_operations               |
| server_transactions             |
| table_distribution_status       |
| table_fragments                 |
| table_info                      |
| table_replicas                  |
| tc_time_track_stats             |
| threadblocks                    |
| threads                         |
| threadstat                      |
| transporters                    |
+---------------------------------+
44 rows in set (0.00 sec)

In NDB 8.0, all ndbinfo tables use the NDB storage engine; however, an ndbinfo entry still appears in the output of SHOW ENGINES and SHOW PLUGINS as described previously.

You can execute SELECT statements against these tables, just as you would normally expect:

mysql> SELECT * FROM memoryusage;
+---------+---------------------+--------+------------+------------+-------------+
| node_id | memory_type         | used   | used_pages | total      | total_pages |
+---------+---------------------+--------+------------+------------+-------------+
|       5 | Data memory         | 753664 |         23 | 1073741824 |       32768 |
|       5 | Index memory        | 163840 |         20 | 1074003968 |      131104 |
|       5 | Long message buffer |   2304 |          9 |   67108864 |      262144 |
|       6 | Data memory         | 753664 |         23 | 1073741824 |       32768 |
|       6 | Index memory        | 163840 |         20 | 1074003968 |      131104 |
|       6 | Long message buffer |   2304 |          9 |   67108864 |      262144 |
+---------+---------------------+--------+------------+------------+-------------+
6 rows in set (0.02 sec)

More complex queries, such as the two following SELECT statements using the memoryusage table, are possible:

mysql> SELECT SUM(used) as 'Data Memory Used, All Nodes'
     >     FROM memoryusage
     >     WHERE memory_type = 'Data memory';
+-----------------------------+
| Data Memory Used, All Nodes |
+-----------------------------+
|                        6460 |
+-----------------------------+
1 row in set (0.37 sec)

mysql> SELECT SUM(max) as 'Total IndexMemory Available'
     >     FROM memoryusage
     >     WHERE memory_type = 'Index memory';
+-----------------------------+
| Total IndexMemory Available |
+-----------------------------+
|                       25664 |
+-----------------------------+
1 row in set (0.33 sec)

ndbinfo table and column names are case-sensitive (as is the name of the ndbinfo database itself). These identifiers are in lowercase. Trying to use the wrong lettercase results in an error, as shown in this example:

mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+
| node_id | uptime | status  | start_phase |
+---------+--------+---------+-------------+
|       1 |  13602 | STARTED |           0 |
|       2 |     16 | STARTED |           0 |
+---------+--------+---------+-------------+
2 rows in set (0.04 sec)

mysql> SELECT * FROM Nodes;
ERROR 1146 (42S02): Table 'ndbinfo.Nodes' doesn't exist

mysqldump ignores the ndbinfo database entirely, and excludes it from any output. This is true even when using the --databases or --all-databases option.

NDB Cluster also maintains tables in the INFORMATION_SCHEMA information database, including the FILES table which contains information about files used for NDB Cluster Disk Data storage, and the ndb_transid_mysql_connection_map table, which shows the relationships between transactions, transaction coordinators, and NDB Cluster API nodes. For more information, see the descriptions of the tables or Section 23.5.15, “INFORMATION_SCHEMA Tables for NDB Cluster”.

23.5.14.1 The ndbinfo arbitrator_validity_detail Table

The arbitrator_validity_detail table shows the view that each data node in the cluster has of the arbitrator. It is a subset of the membership table.

The arbitrator_validity_detail table contains the following columns:

  • node_id

    This node's node ID

  • arbitrator

    Node ID of arbitrator

  • arb_ticket

    Internal identifier used to track arbitration

  • arb_connected

    Whether this node is connected to the arbitrator; either of Yes or No

  • arb_state

    Arbitration state

Notes

The node ID is the same as that reported by ndb_mgm -e "SHOW".

All nodes should show the same arbitrator and arb_ticket values as well as the same arb_state value. Possible arb_state values are ARBIT_NULL, ARBIT_INIT, ARBIT_FIND, ARBIT_PREP1, ARBIT_PREP2, ARBIT_START, ARBIT_RUN, ARBIT_CHOOSE, ARBIT_CRASH, and UNKNOWN.

arb_connected shows whether the current node is connected to the arbitrator.

23.5.14.2 The ndbinfo arbitrator_validity_summary Table

The arbitrator_validity_summary table provides a composite view of the arbitrator with regard to the cluster's data nodes.

The arbitrator_validity_summary table contains the following columns:

  • arbitrator

    Node ID of arbitrator

  • arb_ticket

    Internal identifier used to track arbitration

  • arb_connected

    Whether this arbitrator is connected to the cluster

  • consensus_count

    Number of data nodes that see this node as arbitrator; either of Yes or No

Notes

In normal operations, this table should have only 1 row for any appreciable length of time. If it has more than 1 row for longer than a few moments, then either not all nodes are connected to the arbitrator, or all nodes are connected, but do not agree on the same arbitrator.

The arbitrator column shows the arbitrator's node ID.

arb_ticket is the internal identifier used by this arbitrator.

arb_connected shows whether this node is connected to the cluster as an arbitrator.

23.5.14.3 The ndbinfo backup_id Table

This table provides a way to find the ID of the backup started most recently for this cluster.

The backup_id table contains a single column id, which corresponds to a backup ID taken using the ndb_mgm client START BACKUP command. This table contains a single row.

Example: Assume the following sequence of START BACKUP commands issued in the NDB management client, with no other backups taken since the cluster was first started:

ndb_mgm> START BACKUP
Waiting for completed, this may take several minutes
Node 5: Backup 1 started from node 50
Node 5: Backup 1 started from node 50 completed
 StartGCP: 27894 StopGCP: 27897
 #Records: 2057 #LogRecords: 0
 Data: 51580 bytes Log: 0 bytes
ndb_mgm> START BACKUP 5
Waiting for completed, this may take several minutes
Node 5: Backup 5 started from node 50
Node 5: Backup 5 started from node 50 completed
 StartGCP: 27905 StopGCP: 27908
 #Records: 2057 #LogRecords: 0
 Data: 51580 bytes Log: 0 bytes
ndb_mgm> START BACKUP
Waiting for completed, this may take several minutes
Node 5: Backup 6 started from node 50
Node 5: Backup 6 started from node 50 completed
 StartGCP: 27912 StopGCP: 27915
 #Records: 2057 #LogRecords: 0
 Data: 51580 bytes Log: 0 bytes
ndb_mgm> START BACKUP 3
Connected to Management Server at: localhost:1186
Waiting for completed, this may take several minutes
Node 5: Backup 3 started from node 50
Node 5: Backup 3 started from node 50 completed
 StartGCP: 28149 StopGCP: 28152
 #Records: 2057 #LogRecords: 0
 Data: 51580 bytes Log: 0 bytes
ndb_mgm>

After this, the backup_id table contains the single row shown here, using the mysql client:

mysql> USE ndbinfo;

Database changed
mysql> SELECT * FROM backup_id;
+------+
| id   |
+------+
|    3 |
+------+
1 row in set (0.00 sec)

If no backups can be found, the table contains a single row with 0 as the id value.

The backup_id table was added in NDB 8.0.24.

23.5.14.4 The ndbinfo blocks Table

The blocks table is a static table which simply contains the names and internal IDs of all NDB kernel blocks (see NDB Kernel Blocks). It is for use by the other ndbinfo tables (most of which are actually views) in mapping block numbers to block names for producing human-readable output.

The blocks table contains the following columns:

  • block_number

    Block number

  • block_name

    Block name

Notes

To obtain a list of all block names, simply execute SELECT block_name FROM ndbinfo.blocks. Although this is a static table, its content can vary between different NDB Cluster releases.

23.5.14.5 The ndbinfo cluster_locks Table

The cluster_locks table provides information about current lock requests holding and waiting for locks on NDB tables in an NDB Cluster, and is intended as a companion table to cluster_operations. Information obtain from the cluster_locks table may be useful in investigating stalls and deadlocks.

The cluster_locks table contains the following columns:

  • node_id

    ID of reporting node

  • block_instance

    ID of reporting LDM instance

  • tableid

    ID of table containing this row

  • fragmentid

    ID of fragment containing locked row

  • rowid

    ID of locked row

  • transid

    Transaction ID

  • mode

    Lock request mode

  • state

    Lock state

  • detail

    Whether this is first holding lock in row lock queue

  • op

    Operation type

  • duration_millis

    Milliseconds spent waiting or holding lock

  • lock_num

    ID of lock object

  • waiting_for

    Waiting for lock with this ID

Notes

The table ID (tableid column) is assigned internally, and is the same as that used in other ndbinfo tables. It is also shown in the output of ndb_show_tables.

The transaction ID (transid column) is the identifier generated by the NDB API for the transaction requesting or holding the current lock.

The mode column shows the lock mode; this is always one of S (indicating a shared lock) or X (an exclusive lock). If a transaction holds an exclusive lock on a given row, all other locks on that row have the same transaction ID.

The state column shows the lock state. Its value is always one of H (holding) or W (waiting). A waiting lock request waits for a lock held by a different transaction.

When the detail column contains a * (asterisk character), this means that this lock is the first holding lock in the affected row's lock queue; otherwise, this column is empty. This information can be used to help identify the unique entries in a list of lock requests.

The op column shows the type of operation requesting the lock. This is always one of the values READ, INSERT, UPDATE, DELETE, SCAN, or REFRESH.

The duration_millis column shows the number of milliseconds for which this lock request has been waiting or holding the lock. This is reset to 0 when a lock is granted for a waiting request.

The lock ID (lockid column) is unique to this node and block instance.

The lock state is shown in the lock_state column; if this is W, the lock is waiting to be granted, and the waiting_for column shows the lock ID of the lock object this request is waiting for. Otherwise, the waiting_for column is empty. waiting_for can refer only to locks on the same row, as identified by node_id, block_instance, tableid, fragmentid, and rowid.

23.5.14.6 The ndbinfo cluster_operations Table

The cluster_operations table provides a per-operation (stateful primary key op) view of all activity in the NDB Cluster from the point of view of the local data management (LQH) blocks (see The DBLQH Block).

The cluster_operations table contains the following columns:

  • node_id

    Node ID of reporting LQH block

  • block_instance

    LQH block instance

  • transid

    Transaction ID

  • operation_type

    Operation type (see text for possible values)

  • state

    Operation state (see text for possible values)

  • tableid

    Table ID

  • fragmentid

    Fragment ID

  • client_node_id

    Client node ID

  • client_block_ref

    Client block reference

  • tc_node_id

    Transaction coordinator node ID

  • tc_block_no

    Transaction coordinator block number

  • tc_block_instance

    Transaction coordinator block instance

Notes

The transaction ID is a unique 64-bit number which can be obtained using the NDB API's getTransactionId() method. (Currently, the MySQL Server does not expose the NDB API transaction ID of an ongoing transaction.)

The operation_type column can take any one of the values READ, READ-SH, READ-EX, INSERT, UPDATE, DELETE, WRITE, UNLOCK, REFRESH, SCAN, SCAN-SH, SCAN-EX, or <unknown>.

The state column can have any one of the values ABORT_QUEUED, ABORT_STOPPED, COMMITTED, COMMIT_QUEUED, COMMIT_STOPPED, COPY_CLOSE_STOPPED, COPY_FIRST_STOPPED, COPY_STOPPED, COPY_TUPKEY, IDLE, LOG_ABORT_QUEUED, LOG_COMMIT_QUEUED, LOG_COMMIT_QUEUED_WAIT_SIGNAL, LOG_COMMIT_WRITTEN, LOG_COMMIT_WRITTEN_WAIT_SIGNAL, LOG_QUEUED, PREPARED, PREPARED_RECEIVED_COMMIT, SCAN_CHECK_STOPPED, SCAN_CLOSE_STOPPED, SCAN_FIRST_STOPPED, SCAN_RELEASE_STOPPED, SCAN_STATE_USED, SCAN_STOPPED, SCAN_TUPKEY, STOPPED, TC_NOT_CONNECTED, WAIT_ACC, WAIT_ACC_ABORT, WAIT_AI_AFTER_ABORT, WAIT_ATTR, WAIT_SCAN_AI, WAIT_TUP, WAIT_TUPKEYINFO, WAIT_TUP_COMMIT, or WAIT_TUP_TO_ABORT. (If the MySQL Server is running with ndbinfo_show_hidden enabled, you can view this list of states by selecting from the ndb$dblqh_tcconnect_state table, which is normally hidden.)

You can obtain the name of an NDB table from its table ID by checking the output of ndb_show_tables.

The fragid is the same as the partition number seen in the output of ndb_desc --extra-partition-info (short form -p).

In client_node_id and client_block_ref, client refers to an NDB Cluster API or SQL node (that is, an NDB API client or a MySQL Server attached to the cluster).

The block_instance and tc_block_instance column provide, respectively, the DBLQH and DBTC block instance numbers. You can use these along with the block names to obtain information about specific threads from the threadblocks table.

23.5.14.7 The ndbinfo cluster_transactions Table

The cluster_transactions table shows information about all ongoing transactions in an NDB Cluster.

The cluster_transactions table contains the following columns:

  • node_id

    Node ID of transaction coordinator

  • block_instance

    TC block instance

  • transid

    Transaction ID

  • state

    Operation state (see text for possible values)

  • count_operations

    Number of stateful primary key operations in transaction (includes reads with locks, as well as DML operations)

  • outstanding_operations

    Operations still being executed in local data management blocks

  • inactive_seconds

    Time spent waiting for API

  • client_node_id

    Client node ID

  • client_block_ref

    Client block reference

Notes

The transaction ID is a unique 64-bit number which can be obtained using the NDB API's getTransactionId() method. (Currently, the MySQL Server does not expose the NDB API transaction ID of an ongoing transaction.)

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table.

The state column can have any one of the values CS_ABORTING, CS_COMMITTING, CS_COMMIT_SENT, CS_COMPLETE_SENT, CS_COMPLETING, CS_CONNECTED, CS_DISCONNECTED, CS_FAIL_ABORTED, CS_FAIL_ABORTING, CS_FAIL_COMMITTED, CS_FAIL_COMMITTING, CS_FAIL_COMPLETED, CS_FAIL_PREPARED, CS_PREPARE_TO_COMMIT, CS_RECEIVING, CS_REC_COMMITTING, CS_RESTART, CS_SEND_FIRE_TRIG_REQ, CS_STARTED, CS_START_COMMITTING, CS_START_SCAN, CS_WAIT_ABORT_CONF, CS_WAIT_COMMIT_CONF, CS_WAIT_COMPLETE_CONF, CS_WAIT_FIRE_TRIG_REQ. (If the MySQL Server is running with ndbinfo_show_hidden enabled, you can view this list of states by selecting from the ndb$dbtc_apiconnect_state table, which is normally hidden.)

In client_node_id and client_block_ref, client refers to an NDB Cluster API or SQL node (that is, an NDB API client or a MySQL Server attached to the cluster).

The tc_block_instance column provides the DBTC block instance number. You can use this along with the block name to obtain information about specific threads from the threadblocks table.

23.5.14.8 The ndbinfo config_nodes Table

The config_nodes table shows nodes configured in an NDB Cluster config.ini file. For each node, the table displays a row containing the node ID, the type of node (management node, data node, or API node), and the name or IP address of the host on which the node is configured to run.

This table does not indicate whether a given node is actually running, or whether it is currently connected to the cluster. Information about nodes connected to an NDB Cluster can be obtained from the nodes and processes table.

The config_nodes table contains the following columns:

  • node_id

    The node's ID

  • node_type

    The type of node

  • node_hostname

    The name or IP address of the host on which the node resides

Notes

The node_id column shows the node ID used in the config.ini file for this node; if none is specified, the node ID that would be assigned automatically to this node is displayed.

The node_type column displays one of the following three values:

  • MGM: Management node.

  • NDB: Data node.

  • API: API node; this includes SQL nodes.

The node_hostname column shows the node host as specified in the config.ini file. This can be empty for an API node, if HostName has not been set in the cluster configuration file. If HostName has not been set for a data node in the configuration file, localhost is used here. localhost is also used if HostName has not been specified for a management node.

23.5.14.9 The ndbinfo config_params Table

The config_params table is a static table which provides the names and internal ID numbers of and other information about NDB Cluster configuration parameters. This table can also be used in conjunction with the config_values table for obtaining realtime information about node configuration parameters.

The config_params table contains the following columns:

  • param_number

    The parameter's internal ID number

  • param_name

    The name of the parameter

  • param_description

    A brief description of the parameter

  • param_type

    The parameter's data type

  • param_default

    The parameter's default value, if any

  • param_min

    The parameter's maximum value, if any

  • param_max

    The parameter's minimum value, if any

  • param_mandatory

    This is 1 if the parameter is required, otherwise 0

  • param_status

    Currently unused

Notes

This table is read-only.

Although this is a static table, its content can vary between NDB Cluster installations, since supported parameters can vary due to differences between software releases, cluster hardware configurations, and other factors.

23.5.14.10 The ndbinfo config_values Table

The config_values table provides information about the current state of node configuration parameter values. Each row in the table corresponds to the current value of a parameter on a given node.

The config_values table contains the following columns:

  • node_id

    ID of the node in the cluster

  • config_param

    The parameter's internal ID number

  • config_value

    Current value of the parameter

Notes

This table's config_param column and the config_params table's param_number column use the same parameter identifiers. By joining the two tables on these columns, you can obtain detailed information about desired node configuration parameters. The query shown here provides the current values for all parameters on each data node in the cluster, ordered by node ID and parameter name:

SELECT    v.node_id AS 'Node Id',
          p.param_name AS 'Parameter',
          v.config_value AS 'Value'
FROM      config_values v
JOIN      config_params p
ON        v.config_param=p.param_number
WHERE     p.param_name NOT LIKE '\_\_%'
ORDER BY  v.node_id, p.param_name;

Partial output from the previous query when run on a small example cluster used for simple testing:

+---------+------------------------------------------+----------------+
| Node Id | Parameter                                | Value          |
+---------+------------------------------------------+----------------+
|       2 | Arbitration                              | 1              |
|       2 | ArbitrationTimeout                       | 7500           |
|       2 | BackupDataBufferSize                     | 16777216       |
|       2 | BackupDataDir                            | /home/jon/data |
|       2 | BackupDiskWriteSpeedPct                  | 50             |
|       2 | BackupLogBufferSize                      | 16777216       |

...

|       3 | TotalSendBufferMemory                    | 0              |
|       3 | TransactionBufferMemory                  | 1048576        |
|       3 | TransactionDeadlockDetectionTimeout      | 1200           |
|       3 | TransactionInactiveTimeout               | 4294967039     |
|       3 | TwoPassInitialNodeRestartCopy            | 0              |
|       3 | UndoDataBuffer                           | 16777216       |
|       3 | UndoIndexBuffer                          | 2097152        |
+---------+------------------------------------------+----------------+
248 rows in set (0.02 sec)

The WHERE clause filters out parameters whose names begin with a double underscore (__); these parameters are reserved for testing and other internal uses by the NDB developers, and are not intended for use in a production NDB Cluster.

You can obtain output that is more specific, more detailed, or both by issuing the proper queries. This example provides all types of available information about the NodeId, NoOfReplicas, HostName, DataMemory, IndexMemory, and TotalSendBufferMemory parameters as currently set for all data nodes in the cluster:

SELECT  p.param_name AS Name,
        v.node_id AS Node,
        p.param_type AS Type,
        p.param_default AS 'Default',
        p.param_min AS Minimum,
        p.param_max AS Maximum,
        CASE p.param_mandatory WHEN 1 THEN 'Y' ELSE 'N' END AS 'Required',
        v.config_value AS Current
FROM    config_params p
JOIN    config_values v
ON      p.param_number = v.config_param
WHERE   p. param_name
  IN ('NodeId', 'NoOfReplicas', 'HostName',
      'DataMemory', 'IndexMemory', 'TotalSendBufferMemory')\G

The output from this query when run on a small NDB Cluster with 2 data nodes used for simple testing is shown here (NDB 8.0.18 and later):

*************************** 1. row ***************************
    Name: NodeId
    Node: 2
    Type: unsigned
 Default:
 Minimum: 1
 Maximum: 144
Required: Y
 Current: 2
*************************** 2. row ***************************
    Name: HostName
    Node: 2
    Type: string
 Default: localhost
 Minimum:
 Maximum:
Required: N
 Current: 127.0.0.1
*************************** 3. row ***************************
    Name: TotalSendBufferMemory
    Node: 2
    Type: unsigned
 Default: 0
 Minimum: 262144
 Maximum: 4294967039
Required: N
 Current: 0
*************************** 4. row ***************************
    Name: NoOfReplicas
    Node: 2
    Type: unsigned
 Default: 2
 Minimum: 1
 Maximum: 4
Required: N
 Current: 2
*************************** 5. row ***************************
    Name: DataMemory
    Node: 2
    Type: unsigned
 Default: 102760448
 Minimum: 1048576
 Maximum: 1099511627776
Required: N
 Current: 524288000
*************************** 6. row ***************************
    Name: NodeId
    Node: 3
    Type: unsigned
 Default:
 Minimum: 1
 Maximum: 144
Required: Y
 Current: 3
*************************** 7. row ***************************
    Name: HostName
    Node: 3
    Type: string
 Default: localhost
 Minimum:
 Maximum:
Required: N
 Current: 127.0.0.1
*************************** 8. row ***************************
    Name: TotalSendBufferMemory
    Node: 3
    Type: unsigned
 Default: 0
 Minimum: 262144
 Maximum: 4294967039
Required: N
 Current: 0
*************************** 9. row ***************************
    Name: NoOfReplicas
    Node: 3
    Type: unsigned
 Default: 2
 Minimum: 1
 Maximum: 4
Required: N
 Current: 2
*************************** 10. row ***************************
    Name: DataMemory
    Node: 3
    Type: unsigned
 Default: 102760448
 Minimum: 1048576
 Maximum: 1099511627776
Required: N
 Current: 524288000
10 rows in set (0.01 sec)

23.5.14.11 The ndbinfo counters Table

The counters table provides running totals of events such as reads and writes for specific kernel blocks and data nodes. Counts are kept from the most recent node start or restart; a node start or restart resets all counters on that node. Not all kernel blocks have all types of counters.

The counters table contains the following columns:

  • node_id

    The data node ID

  • block_name

    Name of the associated NDB kernel block (see NDB Kernel Blocks).

  • block_instance

    Block instance

  • counter_id

    The counter's internal ID number; normally an integer between 1 and 10, inclusive.

  • counter_name

    The name of the counter. See text for names of individual counters and the NDB kernel block with which each counter is associated.

  • val

    The counter's value

Notes

Each counter is associated with a particular NDB kernel block.

The OPERATIONS counter is associated with the DBLQH (local query handler) kernel block. A primary-key read counts as one operation, as does a primary-key update. For reads, there is one operation in DBLQH per operation in DBTC. For writes, there is one operation counted per fragment replica.

The ATTRINFO, TRANSACTIONS, COMMITS, READS, LOCAL_READS, SIMPLE_READS, WRITES, LOCAL_WRITES, ABORTS, TABLE_SCANS, and RANGE_SCANS counters are associated with the DBTC (transaction co-ordinator) kernel block.

LOCAL_WRITES and LOCAL_READS are primary-key operations using a transaction coordinator in a node that also holds the primary fragment replica of the record.

The READS counter includes all reads. LOCAL_READS includes only those reads of the primary fragment replica on the same node as this transaction coordinator. SIMPLE_READS includes only those reads in which the read operation is the beginning and ending operation for a given transaction. Simple reads do not hold locks but are part of a transaction, in that they observe uncommitted changes made by the transaction containing them but not of any other uncommitted transactions. Such reads are simple from the point of view of the TC block; since they hold no locks they are not durable, and once DBTC has routed them to the relevant LQH block, it holds no state for them.

ATTRINFO keeps a count of the number of times an interpreted program is sent to the data node. See NDB Protocol Messages, for more information about ATTRINFO messages in the NDB kernel.

The LOCAL_TABLE_SCANS_SENT, READS_RECEIVED, PRUNED_RANGE_SCANS_RECEIVED, RANGE_SCANS_RECEIVED, LOCAL_READS_SENT, CONST_PRUNED_RANGE_SCANS_RECEIVED, LOCAL_RANGE_SCANS_SENT, REMOTE_READS_SENT, REMOTE_RANGE_SCANS_SENT, READS_NOT_FOUND, SCAN_BATCHES_RETURNED, TABLE_SCANS_RECEIVED, and SCAN_ROWS_RETURNED counters are associated with the DBSPJ (select push-down join) kernel block.

The block_name and block_instance columns provide, respectively, the applicable NDB kernel block name and instance number. You can use these to obtain information about specific threads from the threadblocks table.

A number of counters provide information about transporter overload and send buffer sizing when troubleshooting such issues. For each LQH instance, there is one instance of each counter in the following list:

  • LQHKEY_OVERLOAD: Number of primary key requests rejected at the LQH block instance due to transporter overload

  • LQHKEY_OVERLOAD_TC: Count of instances of LQHKEY_OVERLOAD where the TC node transporter was overloaded

  • LQHKEY_OVERLOAD_READER: Count of instances of LQHKEY_OVERLOAD where the API reader (reads only) node was overloaded.

  • LQHKEY_OVERLOAD_NODE_PEER: Count of instances of LQHKEY_OVERLOAD where the next backup data node (writes only) was overloaded

  • LQHKEY_OVERLOAD_SUBSCRIBER: Count of instances of LQHKEY_OVERLOAD where a event subscriber (writes only) was overloaded.

  • LQHSCAN_SLOWDOWNS: Count of instances where a fragment scan batch size was reduced due to scanning API transporter overload.

23.5.14.12 The ndbinfo cpudata Table

The cpudata table provides data about CPU usage during the last second.

The cpustat table contains the following columns:

  • node_id

    Node ID

  • cpu_no

    CPU ID

  • cpu_online

    1 if the CPU is currently online, otherwise 0

  • cpu_userspace_time

    CPU time spent in userspace

  • cpu_idle_time

    CPU time spent idle

  • cpu_system_time

    CPU time spent in system time

  • cpu_interrupt_time

    CPU time spent handling interrupts (hardware and software)

  • cpu_exec_vm_time

    CPU time spent in virtual machine execution

Notes

The cpudata table is available only on Linux and Solaris operating systems.

This table was added in NDB 8.0.23.

23.5.14.13 The ndbinfo cpudata_1sec Table

The cpudata_1sec table provides data about CPU usage per second over the last 20 seconds.

The cpustat table contains the following columns:

  • node_id

    Node ID

  • measurement_id

    Measurement sequence ID; later measurements have lower IDs

  • cpu_no

    CPU ID

  • cpu_online

    1 if the CPU is currently online, otherwise 0

  • cpu_userspace_time

    CPU time spent in userspace

  • cpu_idle_time

    CPU time spent idle

  • cpu_system_time

    CPU time spent in system time

  • cpu_interrupt_time

    CPU time spent handling interrupts (hardware and software)

  • cpu_exec_vm_time

    CPU time spent in virtual machine execution

  • elapsed_time

    Time in microseconds used for this measurement

Notes

The cpudata_1sec table is available only on Linux and Solaris operating systems.

This table was added in NDB 8.0.23.

23.5.14.14 The ndbinfo cpudata_20sec Table

The cpudata_20sec table provides data about CPU usage per 20-second interval over the last 400 seconds.

The cpustat table contains the following columns:

  • node_id

    Node ID

  • measurement_id

    Measurement sequence ID; later measurements have lower IDs

  • cpu_no

    CPU ID

  • cpu_online

    1 if the CPU is currently online, otherwise 0

  • cpu_userspace_time

    CPU time spent in userspace

  • cpu_idle_time

    CPU time spent idle

  • cpu_system_time

    CPU time spent in system time

  • cpu_interrupt_time

    CPU time spent handling interrupts (hardware and software)

  • cpu_exec_vm_time

    CPU time spent in virtual machine execution

  • elapsed_time

    Time in microseconds used for this measurement

Notes

The cpudata_20sec table is available only on Linux and Solaris operating systems.

This table was added in NDB 8.0.23.

23.5.14.15 The ndbinfo cpudata_50ms Table

The cpudata_50ms table provides data about CPU usage per 50-millisecond interval over the last second.

The cpustat table contains the following columns:

  • node_id

    Node ID

  • measurement_id

    Measurement sequence ID; later measurements have lower IDs

  • cpu_no

    CPU ID

  • cpu_online

    1 if the CPU is currently online, otherwise 0

  • cpu_userspace_time

    CPU time spent in userspace

  • cpu_idle_time

    CPU time spent idle

  • cpu_system_time

    CPU time spent in system time

  • cpu_interrupt_time

    CPU time spent handling interrupts (hardware and software)

  • cpu_exec_vm_time

    CPU time spent in virtual machine execution

  • elapsed_time

    Time in microseconds used for this measurement

Notes

The cpudata_50ms table is available only on Linux and Solaris operating systems.

This table was added in NDB 8.0.23.

23.5.14.16 The ndbinfo cpuinfo Table

The cpuinfo table provides information about the CPU on which a given data node executes.

The cpuinfo table contains the following columns:

  • node_id

    Node ID

  • cpu_no

    CPU ID

  • cpu_online

    1 if the CPU is online, otherwise 0

  • core_id

    CPU core ID

  • socket_id

    CPU socket ID

Notes

The cpuinfo table is available on all operating systems supported by NDB, with the exception of MacOS and FreeBSD.

This table was added in NDB 8.0.23.

23.5.14.17 The ndbinfo cpustat Table

The cpustat table provides per-thread CPU statistics gathered each second, for each thread running in the NDB kernel.

The cpustat table contains the following columns:

  • node_id

    ID of the node where the thread is running

  • thr_no

    Thread ID (specific to this node)

  • OS_user

    OS user time

  • OS_system

    OS system time

  • OS_idle

    OS idle time

  • thread_exec

    Thread execution time

  • thread_sleeping

    Thread sleep time

  • thread_spinning

    Thread spin time

  • thread_send

    Thread send time

  • thread_buffer_full

    Thread buffer full time

  • elapsed_time

    Elapsed time

23.5.14.18 The ndbinfo cpustat_50ms Table

The cpustat_50ms table provides raw, per-thread CPU data obtained each 50 milliseconds for each thread running in the NDB kernel.

Like cpustat_1sec and cpustat_20sec, this table shows 20 measurement sets per thread, each referencing a period of the named duration. Thus, cpsustat_50ms provides 1 second of history.

The cpustat_50ms table contains the following columns:

  • node_id

    ID of the node where the thread is running

  • thr_no

    Thread ID (specific to this node)

  • OS_user_time

    OS user time

  • OS_system_time

    OS system time

  • OS_idle_time

    OS idle time

  • exec_time

    Thread execution time

  • sleep_time

    Thread sleep time

  • spin_time

    Thread spin time

  • send_time

    Thread send time

  • buffer_full_time

    Thread buffer full time

  • elapsed_time

    Elapsed time

23.5.14.19 The ndbinfo cpustat_1sec Table

The cpustat-1sec table provides raw, per-thread CPU data obtained each second for each thread running in the NDB kernel.

Like cpustat_50ms and cpustat_20sec, this table shows 20 measurement sets per thread, each referencing a period of the named duration. Thus, cpsustat_1sec provides 20 seconds of history.

The cpustat_1sec table contains the following columns:

  • node_id

    ID of the node where the thread is running

  • thr_no

    Thread ID (specific to this node)

  • OS_user_time

    OS user time

  • OS_system_time

    OS system time

  • OS_idle_time

    OS idle time

  • exec_time

    Thread execution time

  • sleep_time

    Thread sleep time

  • spin_time

    Thread spin time

  • send_time

    Thread send time

  • buffer_full_time

    Thread buffer full time

  • elapsed_time

    Elapsed time

23.5.14.20 The ndbinfo cpustat_20sec Table

The cpustat_20sec table provides raw, per-thread CPU data obtained each 20 seconds, for each thread running in the NDB kernel.

Like cpustat_50ms and cpustat_1sec, this table shows 20 measurement sets per thread, each referencing a period of the named duration. Thus, cpsustat_20sec provides 400 seconds of history.

The cpustat_20sec table contains the following columns:

  • node_id

    ID of the node where the thread is running

  • thr_no

    Thread ID (specific to this node)

  • OS_user_time

    OS user time

  • OS_system_time

    OS system time

  • OS_idle_time

    OS idle time

  • exec_time

    Thread execution time

  • sleep_time

    Thread sleep time

  • spin_time

    Thread spin time

  • send_time

    Thread send time

  • buffer_full_time

    Thread buffer full time

  • elapsed_time

    Elapsed time

23.5.14.21 The ndbinfo dict_obj_info Table

The dict_obj_info table provides information about NDB data dictionary (DICT) objects such as tables and indexes. (The dict_obj_types table can be queried for a list of all the types.) This information includes the object's type, state, parent object (if any), and fully qualified name.

The dict_obj_info table contains the following columns:

  • type

    Type of DICT object; join on dict_obj_types to obtain the name

  • id

    Object identifier; for Disk Data undo log files and data files, this is the same as the value shown in the LOGFILE_GROUP_NUMBER column of the INFORMATION_SCHEMA.FILES table; for undo log files, it also the same as the value shown for the log_id column in the ndbinfo logbuffers and logspaces tables

  • version

    Object version

  • state

    Object state

  • parent_obj_type

    Parent object's type (a dict_obj_types type ID); 0 indicates that the object has no parent

  • parent_obj_id

    Parent object ID (such as a base table); 0 indicates that the object has no parent

  • fq_name

    Fully qualified object name; for a table, this has the form database_name/def/table_name, for a primary key, the form is sys/def/table_id/PRIMARY, and for a unique key it is sys/def/table_id/uk_name$unique

23.5.14.22 The ndbinfo dict_obj_tree Table

The dict_obj_tree table provides a tree-based view of table information from the dict_obj_info table. This is intended priarily for use in testing, but can be useful in visualizing hierachies of NDB database objects.

The dict_obj_tree table contains the following columns:

  • type

    Type of DICT object; join on dict_obj_types to obtain the name of the object type

  • id

    Object identifier; same as the id column in dict_obj_info

    For Disk Data undo log files and data files, this is the same as the value shown in the LOGFILE_GROUP_NUMBER column of the INFORMATION_SCHEMA.FILES table; for undo log files, it also the same as the value shown for the log_id column in the ndbinfo logbuffers and logspaces tables

  • name

    The fully qualified name of the object; the same as the fq_name column in dict_obj_info

    For a table, this is database_name/def/table_name (the same as its parent_name); for an index of any type, this takes the form NDB$INDEX_index_id_CUSTOM

  • parent_type

    The DICT object type of this object's parent object; join on dict_obj_types to obtain the name of the object type

  • parent_id

    Identifier for this object's parent object; the same as the dict_obj_info table's id column

  • parent_name

    Fully qualified name of this object's parent object; the same as the dict_obj_info table's fq_name column

    For a table, this has the form database_name/def/table_name. For an index, the name is sys/def/table_id/index_name. For a primary key, it is sys/def/table_id/PRIMARY, and for a unique key it is sys/def/table_id/uk_name$unique

  • root_type

    The DICT object type of the root object; join on dict_obj_types to obtain the name of the object type

  • root_id

    Identifier for the root object; the same as the dict_obj_info table's id column

  • root_name

    Fully qualified name of the root object; the same as the dict_obj_info table's fq_name column

  • level

    Level of the object in the hierarchy

  • path

    Complete path to the object in the NDB object hierarchy; objects are separated by a right arrow (represented as ->), starting with the root object on the left

  • indented_name

    The name prefixed with a right arrow (represented as ->) with a number of spaces preceding it that correspond to the object's depth in the hierarchy

The path column is useful for obtaining a complete path to a given NDB database object in a single line, whereas the indented_name column can be used to obtain a tree-like layout of complete hierarchy information for a desired object.

Example: Assuming the existence of a test database and no existing table named t1 in this database, execute the following SQL statement:

CREATE TABLE test.t1 (
    a INT PRIMARY KEY,
    b INT,
    UNIQUE KEY(b)
)   ENGINE = NDB;

You can obtain the path to the table just created using the query shown here:

mysql> SELECT path FROM ndbinfo.dict_obj_tree
    -> WHERE name LIKE 'test%t1';
+-------------+
| path        |
+-------------+
| test/def/t1 |
+-------------+
1 row in set (0.14 sec)

You can see the paths to all dependent objects of this table using the path to the table as the root name in a query like this one:

mysql> SELECT path FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/t1';
+----------------------------------------------------------+
| path                                                     |
+----------------------------------------------------------+
| test/def/t1                                              |
| test/def/t1 -> sys/def/13/b                              |
| test/def/t1 -> sys/def/13/b -> NDB$INDEX_15_CUSTOM       |
| test/def/t1 -> sys/def/13/b$unique                       |
| test/def/t1 -> sys/def/13/b$unique -> NDB$INDEX_16_UI    |
| test/def/t1 -> sys/def/13/PRIMARY                        |
| test/def/t1 -> sys/def/13/PRIMARY -> NDB$INDEX_14_CUSTOM |
+----------------------------------------------------------+
7 rows in set (0.16 sec)

To obtain a hierarchical view of the t1 table with all its dependent objects, execute a query similar to this one which selects the indented name of each object having test/def/t1 as the name of its root object:

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/t1';
+----------------------------+
| indented_name              |
+----------------------------+
| test/def/t1                |
|   -> sys/def/13/b          |
|     -> NDB$INDEX_15_CUSTOM |
|   -> sys/def/13/b$unique   |
|     -> NDB$INDEX_16_UI     |
|   -> sys/def/13/PRIMARY    |
|     -> NDB$INDEX_14_CUSTOM |
+----------------------------+
7 rows in set (0.15 sec)

When working with Disk Data tables, note that, in this context, a tablespace or log file group is considered a root object. This means that you must know the name of any tablespace or log file group associated with a given table, or obtain this information from SHOW CREATE TABLE and then querying INFORMATION_SCHEMA.FILES, or similar means as shown here:

mysql> SHOW CREATE TABLE test.dt_1\G
*************************** 1. row ***************************
       Table: dt_1
Create Table: CREATE TABLE `dt_1` (
  `member_id` int unsigned NOT NULL AUTO_INCREMENT,
  `last_name` varchar(50) NOT NULL,
  `first_name` varchar(50) NOT NULL,
  `dob` date NOT NULL,
  `joined` date NOT NULL,
  PRIMARY KEY (`member_id`),
  KEY `last_name` (`last_name`,`first_name`)
) /*!50100 TABLESPACE `ts_1` STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)

mysql> SELECT DISTINCT TABLESPACE_NAME, LOGFILE_GROUP_NAME
    -> FROM INFORMATION_SCHEMA.FILES WHERE TABLESPACE_NAME='ts_1';
+-----------------+--------------------+
| TABLESPACE_NAME | LOGFILE_GROUP_NAME |
+-----------------+--------------------+
| ts_1            | lg_1               |
+-----------------+--------------------+
1 row in set (0.00 sec)

Now you can obtain hierarchical information for the table, tablespace, and log file group like this:

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/dt_1';
+----------------------------+
| indented_name              |
+----------------------------+
| test/def/dt_1              |
|   -> sys/def/23/last_name  |
|     -> NDB$INDEX_25_CUSTOM |
|   -> sys/def/23/PRIMARY    |
|     -> NDB$INDEX_24_CUSTOM |
+----------------------------+
5 rows in set (0.15 sec)

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'ts_1';
+-----------------+
| indented_name   |
+-----------------+
| ts_1            |
|   -> data_1.dat |
|   -> data_2.dat |
+-----------------+
3 rows in set (0.17 sec)

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name LIKE 'lg_1';
+-----------------+
| indented_name   |
+-----------------+
| lg_1            |
|   -> undo_1.log |
|   -> undo_2.log |
+-----------------+
3 rows in set (0.16 sec)

The dict_obj_tree table was added in NDB 8.0.24.

23.5.14.23 The ndbinfo dict_obj_types Table

The dict_obj_types table is a static table listing possible dictionary object types used in the NDB kernel. These are the same types defined by Object::Type in the NDB API.

The dict_obj_types table contains the following columns:

  • type_id

    The type ID for this type

  • type_name

    The name of this type

23.5.14.24 The ndbinfo disk_write_speed_base Table

The disk_write_speed_base table provides base information about the speed of disk writes during LCP, backup, and restore operations.

The disk_write_speed_base table contains the following columns:

  • node_id

    Node ID of this node

  • thr_no

    Thread ID of this LDM thread

  • millis_ago

    Milliseconds since this reporting period ended

  • millis_passed

    Milliseconds elapsed in this reporting period

  • backup_lcp_bytes_written

    Number of bytes written to disk by local checkpoints and backup processes during this period

  • redo_bytes_written

    Number of bytes written to REDO log during this period

  • target_disk_write_speed

    Actual speed of disk writes per LDM thread (base data)

23.5.14.25 The ndbinfo disk_write_speed_aggregate Table

The disk_write_speed_aggregate table provides aggregated information about the speed of disk writes during LCP, backup, and restore operations.

The disk_write_speed_aggregate table contains the following columns:

  • node_id

    Node ID of this node

  • thr_no

    Thread ID of this LDM thread

  • backup_lcp_speed_last_sec

    Number of bytes written to disk by backup and LCP processes in the last second

  • redo_speed_last_sec

    Number of bytes written to REDO log in the last second

  • backup_lcp_speed_last_10sec

    Number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds

  • redo_speed_last_10sec

    Number of bytes written to REDO log per second, averaged over the last 10 seconds

  • std_dev_backup_lcp_speed_last_10sec

    Standard deviation in number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds

  • std_dev_redo_speed_last_10sec

    Standard deviation in number of bytes written to REDO log per second, averaged over the last 10 seconds

  • backup_lcp_speed_last_60sec

    Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds

  • redo_speed_last_60sec

    Number of bytes written to REDO log per second, averaged over the last 10 seconds

  • std_dev_backup_lcp_speed_last_60sec

    Standard deviation in number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds

  • std_dev_redo_speed_last_60sec

    Standard deviation in number of bytes written to REDO log per second, averaged over the last 60 seconds

  • slowdowns_due_to_io_lag

    Number of seconds since last node start that disk writes were slowed due to REDO log I/O lag

  • slowdowns_due_to_high_cpu

    Number of seconds since last node start that disk writes were slowed due to high CPU usage

  • disk_write_speed_set_to_min

    Number of seconds since last node start that disk write speed was set to minimum

  • current_target_disk_write_speed

    Actual speed of disk writes per LDM thread (aggregated)

23.5.14.26 The ndbinfo disk_write_speed_aggregate_node Table

The disk_write_speed_aggregate_node table provides aggregated information per node about the speed of disk writes during LCP, backup, and restore operations.

The disk_write_speed_aggregate_node table contains the following columns:

  • node_id

    Node ID of this node

  • backup_lcp_speed_last_sec

    Number of bytes written to disk by backup and LCP processes in the last second

  • redo_speed_last_sec

    Number of bytes written to REDO log in the last second

  • backup_lcp_speed_last_10sec

    Number of bytes written to disk by backup and LCP processes per second, averaged over the last 10 seconds

  • redo_speed_last_10sec

    Number of bytes written to REDO log per second, averaged over the last 10 seconds

  • backup_lcp_speed_last_60sec

    Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds

  • redo_speed_last_60sec

    Number of bytes written to disk by backup and LCP processes per second, averaged over the last 60 seconds

23.5.14.27 The ndbinfo diskpagebuffer Table

The diskpagebuffer table provides statistics about disk page buffer usage by NDB Cluster Disk Data tables.

The diskpagebuffer table contains the following columns:

  • node_id

    The data node ID

  • block_instance

    Block instance

  • pages_written

    Number of pages written to disk.

  • pages_written_lcp

    Number of pages written by local checkpoints.

  • pages_read

    Number of pages read from disk

  • log_waits

    Number of page writes waiting for log to be written to disk

  • page_requests_direct_return

    Number of requests for pages that were available in buffer

  • page_requests_wait_queue

    Number of requests that had to wait for pages to become available in buffer

  • page_requests_wait_io

    Number of requests that had to be read from pages on disk (pages were unavailable in buffer)

Notes

You can use this table with NDB Cluster Disk Data tables to determine whether DiskPageBufferMemory is sufficiently large to allow data to be read from the buffer rather from disk; minimizing disk seeks can help improve performance of such tables.

You can determine the proportion of reads from DiskPageBufferMemory to the total number of reads using a query such as this one, which obtains this ratio as a percentage:

SELECT
  node_id,
  100 * page_requests_direct_return /
    (page_requests_direct_return + page_requests_wait_io)
      AS hit_ratio
FROM ndbinfo.diskpagebuffer;

The result from this query should be similar to what is shown here, with one row for each data node in the cluster (in this example, the cluster has 4 data nodes):

+---------+-----------+
| node_id | hit_ratio |
+---------+-----------+
|       5 |   97.6744 |
|       6 |   97.6879 |
|       7 |   98.1776 |
|       8 |   98.1343 |
+---------+-----------+
4 rows in set (0.00 sec)

hit_ratio values approaching 100% indicate that only a very small number of reads are being made from disk rather than from the buffer, which means that Disk Data read performance is approaching an optimum level. If any of these values are less than 95%, this is a strong indicator that the setting for DiskPageBufferMemory needs to be increased in the config.ini file.

Note

A change in DiskPageBufferMemory requires a rolling restart of all of the cluster's data nodes before it takes effect.

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table. Using this information, you can obtain information about disk page buffer metrics relating to individual threads; an example query using LIMIT 1 to limit the output to a single thread is shown here:

mysql> SELECT
     >   node_id, thr_no, block_name, thread_name, pages_written,
     >   pages_written_lcp, pages_read, log_waits,
     >   page_requests_direct_return, page_requests_wait_queue,
     >   page_requests_wait_io
     > FROM ndbinfo.diskpagebuffer
     >   INNER JOIN ndbinfo.threadblocks USING (node_id, block_instance)
     >   INNER JOIN ndbinfo.threads USING (node_id, thr_no)
     > WHERE block_name = 'PGMAN' LIMIT 1\G
*************************** 1. row ***************************
                    node_id: 1
                     thr_no: 1
                 block_name: PGMAN
                thread_name: rep
              pages_written: 0
          pages_written_lcp: 0
                 pages_read: 1
                  log_waits: 0
page_requests_direct_return: 4
   page_requests_wait_queue: 0
      page_requests_wait_io: 1
1 row in set (0.01 sec)

23.5.14.28 The ndbinfo diskstat Table

The diskstat table provides information about writes to Disk Data tablespaces during the past 1 second.

The diskstat table contains the following columns:

  • node_id

    Node ID of this node

  • block_instance

    ID of reporting instance of PGMAN

  • pages_made_dirty

    Number of pages made dirty during the past second

  • reads_issued

    Reads issued during the past second

  • reads_completed

    Reads completed during the past second

  • writes_issued

    Writes issued during the past second

  • writes_completed

    Writes completed during the past second

  • log_writes_issued

    Number of times a page write has required a log write during the past second

  • log_writes_completed

    Number of log writes completed during the last second

  • get_page_calls_issued

    Number of get_page() calls issued during the past second

  • get_page_reqs_issued

    Number of times that a get_page() call has resulted in a wait for I/O or completion of I/O already begun during the past second

  • get_page_reqs_completed

    Number of get_page() calls waiting for I/O or I/O completion that have completed during the past second

Notes

Each row in this table corresponds to an instance of PGMAN; there is one such instance per LDM thread plus an additional instance for each data node.

The diskstat table was added in NDB 8.0.19.

23.5.14.29 The ndbinfo diskstats_1sec Table

The diskstats_1sec table provides information about writes to Disk Data tablespaces over the past 20 seconds.

The diskstat table contains the following columns:

  • node_id

    Node ID of this node

  • block_instance

    ID of reporting instance of PGMAN

  • pages_made_dirty

    Pages made dirty during the designated 1-second interval

  • reads_issued

    Reads issued during the designated 1-second interval

  • reads_completed

    Reads completed during the designated 1-second interval

  • writes_issued

    Writes issued during the designated 1-second interval

  • writes_completed

    Writes completed during the designated 1-second interval

  • log_writes_issued

    Number of times a page write has required a log write during the designated 1-second interval

  • log_writes_completed

    Number of log writes completed during the designated 1-second interval

  • get_page_calls_issued

    Number of get_page() calls issued during the designated 1-second interval

  • get_page_reqs_issued

    Number of times that a get_page() call has resulted in a wait for I/O or completion of I/O already begun during the designated 1-second interval

  • get_page_reqs_completed

    Number of get_page() calls waiting for I/O or I/O completion that have completed during the designated 1-second interval

  • seconds_ago

    Number of 1-second intervals in the past of the interval to which this row applies

Notes

Each row in this table corresponds to an instance of PGMAN during a 1-second interval occurring from 0 to 19 seconds ago; there is one such instance per LDM thread plus an additional instance for each data node.

The diskstats_1sec table was added in NDB 8.0.19.

23.5.14.30 The ndbinfo error_messages Table

The error_messages table provides information about

The error_messages table contains the following columns:

  • error_code

    Numeric error code

  • error_description

    Description of error

  • error_status

    Error status code

  • error_classification

    Error classification code

Notes

error_code is a numeric NDB error code. This is the same error code that can be supplied to ndb_perror (or, prior to NDB 8.0.13, to perror --ndb).

error_description provides a basic description of the condition causing the error.

The error_status column provides status information relating to the error. Possible values for this column are listed here:

  • No error

  • Illegal connect string

  • Illegal server handle

  • Illegal reply from server

  • Illegal number of nodes

  • Illegal node status

  • Out of memory

  • Management server not connected

  • Could not connect to socket

  • Start failed

  • Stop failed

  • Restart failed

  • Could not start backup

  • Could not abort backup

  • Could not enter single user mode

  • Could not exit single user mode

  • Failed to complete configuration change

  • Failed to get configuration

  • Usage error

  • Success

  • Permanent error

  • Temporary error

  • Unknown result

  • Temporary error, restart node

  • Permanent error, external action needed

  • Ndbd file system error, restart node initial

  • Unknown

The error_classification column shows the error classification. See NDB Error Classifications, for information about classification codes and their meanings.

23.5.14.31 The ndbinfo hwinfo Table

The hwinfo table provides information about the hardware on which a given data node executes.

The hwinfo table contains the following columns:

  • node_id

    Node ID

  • cpu_cnt_max

    Number of processors on this host

  • cpu_cnt

    Number of processors available to this node

  • num_cpu_cores

    Number of CPU cores on this host

  • num_cpu_sockets

    Number of CPU sockets on this host

  • HW_memory_size

    Amount of memory available on this host

  • model_name

    CPU model name

Notes

The hwinfo table is available on all operating systems supported by NDB.

This table was added in NDB 8.0.23.

23.5.14.32 The ndbinfo locks_per_fragment Table

The locks_per_fragment table provides information about counts of lock claim requests, and the outcomes of these requests on a per-fragment basis, serving as a companion table to operations_per_fragment and memory_per_fragment. This table also shows the total time spent waiting for locks successfully and unsuccessfully since fragment or table creation, or since the most recent restart.

The locks_per_fragment table contains the following columns:

  • fq_name

    Fully qualified table name

  • parent_fq_name

    Fully qualified name of parent object

  • type

    Table type; see text for possible values

  • table_id

    Table ID

  • node_id

    Reporting node ID

  • block_instance

    LDM instance ID

  • fragment_num

    Fragment identifier

  • ex_req

    Exclusive lock requests started

  • ex_imm_ok

    Exclusive lock requests immediately granted

  • ex_wait_ok

    Exclusive lock requests granted following wait

  • ex_wait_fail

    Exclusive lock requests not granted

  • sh_req

    Shared lock requests started

  • sh_imm_ok

    Shared lock requests immediately granted

  • sh_wait_ok

    Shared lock requests granted following wait

  • sh_wait_fail

    Shared lock requests not granted

  • wait_ok_millis

    Time spent waiting for lock requests that were granted, in milliseconds

  • wait_fail_millis

    Time spent waiting for lock requests that failed, in milliseconds

Notes

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table.

fq_name is a fully qualified database object name in database/schema/name format, such as test/def/t1 or sys/def/10/b$unique.

parent_fq_name is the fully qualified name of this object's parent object (table).

table_id is the table's internal ID generated by NDB. This is the same internal table ID shown in other ndbinfo tables; it is also visible in the output of ndb_show_tables.

The type column shows the type of table. This is always one of System table, User table, Unique hash index, Hash index, Unique ordered index, Ordered index, Hash index trigger, Subscription trigger, Read only constraint, Index trigger, Reorganize trigger, Tablespace, Log file group, Data file, Undo file, Hash map, Foreign key definition, Foreign key parent trigger, Foreign key child trigger, or Schema transaction.

The values shown in all of the columns ex_req, ex_req_imm_ok, ex_wait_ok, ex_wait_fail, sh_req, sh_req_imm_ok, sh_wait_ok, and sh_wait_fail represent cumulative numbers of requests since the table or fragment was created, or since the last restart of this node, whichever of these occurred later. This is also true for the time values shown in the wait_ok_millis and wait_fail_millis columns.

Every lock request is considered either to be in progress, or to have completed in some way (that is, to have succeeded or failed). This means that the following relationships are true:

ex_req >= (ex_req_imm_ok + ex_wait_ok + ex_wait_fail)

sh_req >= (sh_req_imm_ok + sh_wait_ok + sh_wait_fail)

The number of requests currently in progress is the current number of incomplete requests, which can be found as shown here:

[exclusive lock requests in progress] =
    ex_req - (ex_req_imm_ok + ex_wait_ok + ex_wait_fail)

[shared lock requests in progress] =
    sh_req - (sh_req_imm_ok + sh_wait_ok + sh_wait_fail)

A failed wait indicates an aborted transaction, but the abort may or may not be caused by a lock wait timeout. You can obtain the total number of aborts while waiting for locks as shown here:

[aborts while waiting for locks] = ex_wait_fail + sh_wait_fail

23.5.14.33 The ndbinfo logbuffers Table

The logbuffer table provides information on NDB Cluster log buffer usage.

The logbuffers table contains the following columns:

  • node_id

    The ID of this data node.

  • log_type

    Type of log. One of: REDO, DD-UNDO, BACKUP-DATA, or BACKUP-LOG.

  • log_id

    The log ID; for Disk Data undo log files, this is the same as the value shown in the LOGFILE_GROUP_NUMBER column of the INFORMATION_SCHEMA.FILES tableas well as the value shown for the log_id column of the ndbinfo logspaces table

  • log_part

    The log part number

  • total

    Total space available for this log

  • used

    Space used by this log

Notes

logbuffers table rows reflecting two additional log types are available when performing an NDB backup. One of these rows has the log type BACKUP-DATA, which shows the amount of data buffer used during backup to copy fragments to backup files. The other row has the log type BACKUP-LOG, which displays the amount of log buffer used during the backup to record changes made after the backup has started. One each of these log_type rows is shown in the logbuffers table for each data node in the cluster. These rows are not present unless an NDB backup is currently being performed.

23.5.14.34 The ndbinfo logspaces Table

This table provides information about NDB Cluster log space usage.

The logspaces table contains the following columns:

  • node_id

    The ID of this data node.

  • log_type

    Type of log; one of: REDO or DD-UNDO.

  • node_id

    The log ID; for Disk Data undo log files, this is the same as the value shown in the LOGFILE_GROUP_NUMBER column of the INFORMATION_SCHEMA.FILES table, as well as the value shown for the log_id column of the ndbinfo logbuffers table

  • log_part

    The log part number.

  • total

    Total space available for this log.

  • used

    Space used by this log.

23.5.14.35 The ndbinfo membership Table

The membership table describes the view that each data node has of all the others in the cluster, including node group membership, president node, arbitrator, arbitrator successor, arbitrator connection states, and other information.

The membership table contains the following columns:

  • node_id

    This node's node ID

  • group_id

    Node group to which this node belongs

  • left node

    Node ID of the previous node

  • right_node

    Node ID of the next node

  • president

    President's node ID

  • successor

    Node ID of successor to president

  • succession_order

    Order in which this node succeeds to presidency

  • Conf_HB_order

    -

  • arbitrator

    Node ID of arbitrator

  • arb_ticket

    Internal identifier used to track arbitration

  • arb_state

    Arbitration state

  • arb_connected

    Whether this node is connected to the arbitrator; either of Yes or No

  • connected_rank1_arbs

    Connected arbitrators of rank 1

  • connected_rank2_arbs

    Connected arbitrators of rank 1

Notes

The node ID and node group ID are the same as reported by ndb_mgm -e "SHOW".

left_node and right_node are defined in terms of a model that connects all data nodes in a circle, in order of their node IDs, similar to the ordering of the numbers on a clock dial, as shown here:

Figure 23.27 Circular Arrangement of NDB Cluster Nodes

Content is described in the surrounding text.

In this example, we have 8 data nodes, numbered 5, 6, 7, 8, 12, 13, 14, and 15, ordered clockwise in a circle. We determine left and right from the interior of the circle. The node to the left of node 5 is node 15, and the node to the right of node 5 is node 6. You can see all these relationships by running the following query and observing the output:

mysql> SELECT node_id,left_node,right_node
    -> FROM ndbinfo.membership;
+---------+-----------+------------+
| node_id | left_node | right_node |
+---------+-----------+------------+
|       5 |        15 |          6 |
|       6 |         5 |          7 |
|       7 |         6 |          8 |
|       8 |         7 |         12 |
|      12 |         8 |         13 |
|      13 |        12 |         14 |
|      14 |        13 |         15 |
|      15 |        14 |          5 |
+---------+-----------+------------+
8 rows in set (0.00 sec)

The designations left and right are used in the event log in the same way.

The president node is the node viewed by the current node as responsible for setting an arbitrator (see NDB Cluster Start Phases). If the president fails or becomes disconnected, the current node expects the node whose ID is shown in the successor column to become the new president. The succession_order column shows the place in the succession queue that the current node views itself as having.

In a normal NDB Cluster, all data nodes should see the same node as president, and the same node (other than the president) as its successor. In addition, the current president should see itself as 1 in the order of succession, the successor node should see itself as 2, and so on.

All nodes should show the same arb_ticket values as well as the same arb_state values. Possible arb_state values are ARBIT_NULL, ARBIT_INIT, ARBIT_FIND, ARBIT_PREP1, ARBIT_PREP2, ARBIT_START, ARBIT_RUN, ARBIT_CHOOSE, ARBIT_CRASH, and UNKNOWN.

arb_connected shows whether this node is connected to the node shown as this node's arbitrator.

The connected_rank1_arbs and connected_rank2_arbs columns each display a list of 0 or more arbitrators having an ArbitrationRank equal to 1, or to 2, respectively.

Note

Both management nodes and API nodes are eligible to become arbitrators.

23.5.14.36 The ndbinfo memoryusage Table

Querying this table provides information similar to that provided by the ALL REPORT MemoryUsage command in the ndb_mgm client, or logged by ALL DUMP 1000.

The memoryusage table contains the following columns:

  • node_id

    The node ID of this data node.

  • memory_type

    One of Data memory, Index memory, or Long message buffer.

  • used

    Number of bytes currently used for data memory or index memory by this data node.

  • used_pages

    Number of pages currently used for data memory or index memory by this data node; see text.

  • total

    Total number of bytes of data memory or index memory available for this data node; see text.

  • total_pages

    Total number of memory pages available for data memory or index memory on this data node; see text.

Notes

The total column represents the total amount of memory in bytes available for the given resource (data memory or index memory) on a particular data node. This number should be approximately equal to the setting of the corresponding configuration parameter in the config.ini file.

Suppose that the cluster has 2 data nodes having node IDs 5 and 6, and the config.ini file contains the following:

[ndbd default]
DataMemory = 1G
IndexMemory = 1G

Suppose also that the value of the LongMessageBuffer configuration parameter is allowed to assume its default (64 MB).

The following query shows approximately the same values:

mysql> SELECT node_id, memory_type, total
     > FROM ndbinfo.memoryusage;
+---------+---------------------+------------+
| node_id | memory_type         | total      |
+---------+---------------------+------------+
|       5 | Data memory         | 1073741824 |
|       5 | Index memory        | 1074003968 |
|       5 | Long message buffer |   67108864 |
|       6 | Data memory         | 1073741824 |
|       6 | Index memory        | 1074003968 |
|       6 | Long message buffer |   67108864 |
+---------+---------------------+------------+
6 rows in set (0.00 sec)

In this case, the total column values for index memory are slightly higher than the value set of IndexMemory due to internal rounding.

For the used_pages and total_pages columns, resources are measured in pages, which are 32K in size for DataMemory and 8K for IndexMemory. For long message buffer memory, the page size is 256 bytes.

23.5.14.37 The ndbinfo memory_per_fragment Table

The memory_per_fragment table provides information about the usage of memory by individual fragments.

The memory_per_fragment table contains the following columns:

  • fq_name

    Name of this fragment

  • parent_fq_name

    Name of this fragment's parent

  • type

    Type of object; see text for possible values

  • table_id

    Table ID for this table

  • node_id

    Node ID for this node

  • block_instance

    Kernel block instance ID

  • fragment_num

    Fragment ID (number)

  • fixed_elem_alloc_bytes

    Number of bytes allocated for fixed-sized elements

  • fixed_elem_free_bytes

    Free bytes remaining in pages allocated to fixed-size elements

  • fixed_elem_size_bytes

    Length of each fixed-size element in bytes

  • fixed_elem_count

    Number of fixed-size elements

  • fixed_elem_free_count

    Number of free rows for fixed-size elements

  • var_elem_alloc_bytes

    Number of bytes allocated for variable-size elements

  • var_elem_free_bytes

    Free bytes remaining in pages allocated to variable-size elements

  • var_elem_count

    Number of variable-size elements

  • hash_index_alloc_bytes

    Number of bytes allocated to hash indexes

Notes

The type column from this table shows the dictionary object type used for this fragment (Object::Type, in the NDB API), and can take any one of the values shown in the following list:

  • System table

  • User table

  • Unique hash index

  • Hash index

  • Unique ordered index

  • Ordered index

  • Hash index trigger

  • Subscription trigger

  • Read only constraint

  • Index trigger

  • Reorganize trigger

  • Tablespace

  • Log file group

  • Data file

  • Undo file

  • Hash map

  • Foreign key definition

  • Foreign key parent trigger

  • Foreign key child trigger

  • Schema transaction

You can also obtain this list by executing SELECT * FROM ndbinfo.dict_obj_types in the mysql client.

The block_instance column provides the NDB kernel block instance number. You can use this to obtain information about specific threads from the threadblocks table.

23.5.14.38 The ndbinfo nodes Table

This table contains information on the status of data nodes. For each data node that is running in the cluster, a corresponding row in this table provides the node's node ID, status, and uptime. For nodes that are starting, it also shows the current start phase.

The nodes table contains the following columns:

  • node_id

    The data node's unique node ID in the cluster.

  • uptime

    Time since the node was last started, in seconds.

  • status

    Current status of the data node; see text for possible values.

  • start_phase

    If the data node is starting, the current start phase.

  • config_generation

    The version of the cluster configuration file in use on this data node.

Notes

The uptime column shows the time in seconds that this node has been running since it was last started or restarted. This is a BIGINT value. This figure includes the time actually needed to start the node; in other words, this counter starts running the moment that ndbd or ndbmtd is first invoked; thus, even for a node that has not yet finished starting, uptime may show a nonzero value.

The status column shows the node's current status. This is one of: NOTHING, CMVMI, STARTING, STARTED, SINGLEUSER, STOPPING_1, STOPPING_2, STOPPING_3, or STOPPING_4. When the status is STARTING, you can see the current start phase in the start_phase column (see later in this section). SINGLEUSER is displayed in the status column for all data nodes when the cluster is in single user mode (see Section 23.5.6, “NDB Cluster Single User Mode”). Seeing one of the STOPPING states does not necessarily mean that the node is shutting down but can mean rather that it is entering a new state. For example, if you put the cluster in single user mode, you can sometimes see data nodes report their state briefly as STOPPING_2 before the status changes to SINGLEUSER.

The start_phase column uses the same range of values as those used in the output of the ndb_mgm client node_id STATUS command (see Section 23.5.1, “Commands in the NDB Cluster Management Client”). If the node is not currently starting, then this column shows 0. For a listing of NDB Cluster start phases with descriptions, see Section 23.5.4, “Summary of NDB Cluster Start Phases”.

The config_generation column shows which version of the cluster configuration is in effect on each data node. This can be useful when performing a rolling restart of the cluster in order to make changes in configuration parameters. For example, from the output of the following SELECT statement, you can see that node 3 is not yet using the latest version of the cluster configuration (6) although nodes 1, 2, and 4 are doing so:

mysql> USE ndbinfo;
Database changed
mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+
| node_id | uptime | status  | start_phase | config_generation |
+---------+--------+---------+-------------+-------------------+
|       1 |  10462 | STARTED |           0 |                 6 |
|       2 |  10460 | STARTED |           0 |                 6 |
|       3 |  10457 | STARTED |           0 |                 5 |
|       4 |  10455 | STARTED |           0 |                 6 |
+---------+--------+---------+-------------+-------------------+
2 rows in set (0.04 sec)

Therefore, for the case just shown, you should restart node 3 to complete the rolling restart of the cluster.

Nodes that are stopped are not accounted for in this table. Suppose that you have an NDB Cluster with 4 data nodes (node IDs 1, 2, 3 and 4), and all nodes are running normally, then this table contains 4 rows, 1 for each data node:

mysql> USE ndbinfo;
Database changed
mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+
| node_id | uptime | status  | start_phase | config_generation |
+---------+--------+---------+-------------+-------------------+
|       1 |  11776 | STARTED |           0 |                 6 |
|       2 |  11774 | STARTED |           0 |                 6 |
|       3 |  11771 | STARTED |           0 |                 6 |
|       4 |  11769 | STARTED |           0 |                 6 |
+---------+--------+---------+-------------+-------------------+
4 rows in set (0.04 sec)

If you shut down one of the nodes, only the nodes that are still running are represented in the output of this SELECT statement, as shown here:

ndb_mgm> 2 STOP
Node 2: Node shutdown initiated
Node 2: Node shutdown completed.
Node 2 has shutdown.
mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+
| node_id | uptime | status  | start_phase | config_generation |
+---------+--------+---------+-------------+-------------------+
|       1 |  11807 | STARTED |           0 |                 6 |
|       3 |  11802 | STARTED |           0 |                 6 |
|       4 |  11800 | STARTED |           0 |                 6 |
+---------+--------+---------+-------------+-------------------+
3 rows in set (0.02 sec)

23.5.14.39 The ndbinfo operations_per_fragment Table

The operations_per_fragment table provides information about the operations performed on individual fragments and fragment replicas, as well as about some of the results from these operations.

The operations_per_fragment table contains the following columns:

  • fq_name

    Name of this fragment

  • parent_fq_name

    Name of this fragment's parent

  • type

    Type of object; see text for possible values

  • table_id

    Table ID for this table

  • node_id

    Node ID for this node

  • block_instance

    Kernel block instance ID

  • fragment_num

    Fragment ID (number)

  • tot_key_reads

    Total number of key reads for this fragment replica

  • tot_key_inserts

    Total number of key inserts for this fragment replica

  • tot_key_updates

    total number of key updates for this fragment replica

  • tot_key_writes

    Total number of key writes for this fragment replica

  • tot_key_deletes

    Total number of key deletes for this fragment replica

  • tot_key_refs

    Number of key operations refused

  • tot_key_attrinfo_bytes

    Total size of all attrinfo attributes

  • tot_key_keyinfo_bytes

    Total size of all keyinfo attributes

  • tot_key_prog_bytes

    Total size of all interpreted programs carried by attrinfo attributes

  • tot_key_inst_exec

    Total number of instructions executed by interpreted programs for key operations

  • tot_key_bytes_returned

    Total size of all data and metadata returned from key read operations

  • tot_frag_scans

    Total number of scans performed on this fragment replica

  • tot_scan_rows_examined

    Total number of rows examined by scans

  • tot_scan_rows_returned

    Total number of rows returned to client

  • tot_scan_bytes_returned

    Total size of data and metadata returned to the client

  • tot_scan_prog_bytes

    Total size of interpreted programs for scan operations

  • tot_scan_bound_bytes

    Total size of all bounds used in ordered index scans

  • tot_scan_inst_exec

    Total number of instructions executed for scans

  • tot_qd_frag_scans

    Number of times that scans of this fragment replica have been queued

  • conc_frag_scans

    Number of scans currently active on this fragment replica (excluding queued scans)

  • conc_qd_frag_scans

    Number of scans currently queued for this fragment replica

  • tot_commits

    Total number of row changes committed to this fragment replica

Notes

The fq_name contains the fully qualified name of the schema object to which this fragment replica belongs. This currently has the following formats:

  • Base table: DbName/def/TblName

  • BLOB table: DbName/def/NDB$BLOB_BaseTblId_ColNo

  • Ordered index: sys/def/BaseTblId/IndexName

  • Unique index: sys/def/BaseTblId/IndexName$unique

The $unique suffix shown for unique indexes is added by mysqld; for an index created by a different NDB API client application, this may differ, or not be present.

The syntax just shown for fully qualified object names is an internal interface which is subject to change in future releases.

Consider a table t1 created and modified by the following SQL statements:

CREATE DATABASE mydb;

USE mydb;

CREATE TABLE t1 (
  a INT NOT NULL,
  b INT NOT NULL,
  t TEXT NOT NULL,
  PRIMARY KEY (b)
) ENGINE=ndbcluster;

CREATE UNIQUE INDEX ix1 ON t1(b) USING HASH;

If t1 is assigned table ID 11, this yields the fq_name values shown here:

  • Base table: mydb/def/t1

  • BLOB table: mydb/def/NDB$BLOB_11_2

  • Ordered index (primary key): sys/def/11/PRIMARY

  • Unique index: sys/def/11/ix1$unique

For indexes or BLOB tables, the parent_fq_name column contains the fq_name of the corresponding base table. For base tables, this column is always NULL.

The type column shows the schema object type used for this fragment, which can take any one of the values System table, User table, Unique hash index, or Ordered index. BLOB tables are shown as User table.

The table_id column value is unique at any given time, but can be reused if the corresponding object has been deleted. The same ID can be seen using the ndb_show_tables utility.

The block_instance column shows which LDM instance this fragment replica belongs to. You can use this to obtain information about specific threads from the threadblocks table. The first such instance is always numbered 0.

Since there are typically two fragment replicas, and assuming that this is so, each fragment_num value should appear twice in the table, on two different data nodes from the same node group.

Since NDB does not use single-key access for ordered indexes, the counts for tot_key_reads, tot_key_inserts, tot_key_updates, tot_key_writes, and tot_key_deletes are not incremented by ordered index operations.

Note

When using tot_key_writes, you should keep in mind that a write operation in this context updates the row if the key exists, and inserts a new row otherwise. (One use of this is in the NDB implementation of the REPLACE SQL statement.)

The tot_key_refs column shows the number of key operations refused by the LDM. Generally, such a refusal is due to duplicate keys (inserts), Key not found errors (updates, deletes, and reads), or the operation was rejected by an interpreted program used as a predicate on the row matching the key.

The attrinfo and keyinfo attributes counted by the tot_key_attrinfo_bytes and tot_key_keyinfo_bytes columns are attributes of an LQHKEYREQ signal (see The NDB Communication Protocol) used to initiate a key operation by the LDM. An attrinfo typically contains tuple field values (inserts and updates) or projection specifications (for reads); keyinfo contains the primary or unique key needed to locate a given tuple in this schema object.

The value shown by tot_frag_scans includes both full scans (that examine every row) and scans of subsets. Unique indexes and BLOB tables are never scanned, so this value, like other scan-related counts, is 0 for fragment replicas of these.

tot_scan_rows_examined may display less than the total number of rows in a given fragment replica, since ordered index scans can limited by bounds. In addition, a client may choose to end a scan before all potentially matching rows have been examined; this occurs when using an SQL statement containing a LIMIT or EXISTS clause, for example. tot_scan_rows_returned is always less than or equal to tot_scan_rows_examined.

tot_scan_bytes_returned includes, in the case of pushed joins, projections returned to the DBSPJ block in the NDB kernel.

tot_qd_frag_scans can be effected by the setting for the MaxParallelScansPerFragment data node configuration parameter, which limits the number of scans that may execute concurrently on a single fragment replica.

23.5.14.40 The ndbinfo pgman_time_track_stats Table

This table provides information regarding the latency of disk operations for NDB Cluster Disk Data tablespaces.

The pgman_time_track_stats table contains the following columns:

  • node_id

    Unique node ID of this node in the cluster

  • block_number

    Block number (from blocks table)

  • block_instance

    Block instance number

  • upper_bound

    Upper bound

  • page_reads

    Page read latency (ms)

  • page_writes

    Page write latency (ms)

  • log_waits

    Log wait latency (ms)

  • get_page

    Latency of get_page() calls (ms)

Notes

The read latency (page_reads column) measures the time from when the read request is sent to the file system thread until the read is complete and has been reported back to the execution thread. The write latency (page_writes) is calculated in a similar fashion. The size of the page read to or written from a Disk Data tablespace is always 32 KB.

Log wait latency (log_waits column) is the length of time a page write must wait for the undo log to be flushed, which must be done prior to each page write.

The pgman_time_track_stats table was added in NDB 8.0.19.

23.5.14.41 The ndbinfo processes Table

This table contains information about NDB Cluster node processes; each node is represented by the row in the table. Only nodes that are connected to the cluster are shown in this table. You can obtain information about nodes that are configured but not connected to the cluster from the nodes and config_nodes tables.

The processes table contains the following columns:

  • node_id

    The node's unique node ID in the cluster

  • node_type

    Type of node (management, data, or API node; see text)

  • node_version

    Version of the NDB software program running on this node.

  • process_id

    This node's process ID

  • angel_process_id

    Process ID of this node's angel process

  • process_name

    Name of the executable

  • service_URI

    Service URI of this node (see text)

Notes

node_id is the ID assigned to this node in the cluster.

The node_type column displays one of the following three values:

  • MGM: Management node.

  • NDB: Data node.

  • API: API or SQL node.

For an executable shipped with the NDB Cluster distribution, node_version shows the software Cluster version string, such as 8.0.23-ndb-8.0.23.

process_id is the node executable's process ID as shown by the host operating system using a process display application such as top on Linux, or the Task Manager on Windows platforms.

angel_process_id is the system process ID for the node's angel process, which ensures that a data node or SQL is automatically restarted in cases of failures. For management nodes and API nodes other than SQL nodes, the value of this column is NULL.

The process_name column shows the name of the running executable. For management nodes, this is ndb_mgmd. For data nodes, this is ndbd (single-threaded) or ndbmtd (multithreaded). For SQL nodes, this is mysqld. For other types of API nodes, it is the name of the executable program connected to the cluster; NDB API applications can set a custom value for this using Ndb_cluster_connection::set_name().

service_URI shows the service network address. For management nodes and data nodes, the scheme used is ndb://. For SQL nodes, this is mysql://. By default, API nodes other than SQL nodes use ndb:// for the scheme; NDB API applications can set this to a custom value using Ndb_cluster_connection::set_service_uri(). regardless of the node type, the scheme is followed by the IP address used by the NDB transporter for the node in question. For management nodes and SQL nodes, this address includes the port number (usually 1186 for management nodes and 3306 for SQL nodes). If the SQL node was started with the bind_address system variable set, this address is used instead of the transporter address, unless the bind address is set to *, 0.0.0.0, or ::.

Additional path information may be included in the service_URI value for an SQL node reflecting various configuration options. For example, mysql://198.51.100.3/tmp/mysql.sock indicates that the SQL node was started with the skip_networking system variable enabled, and mysql://198.51.100.3:3306/?server-id=1 shows that replication is enabled for this SQL node.

23.5.14.42 The ndbinfo resources Table

This table provides information about data node resource availability and usage.

These resources are sometimes known as super-pools.

The resources table contains the following columns:

  • node_id

    The unique node ID of this data node.

  • resource_name

    Name of the resource; see text.

  • reserved

    The amount reserved for this resource.

  • used

    The amount actually used by this resource.

  • max

    The maximum amount of this resource used, since the node was last started.

Notes

The resource_name can be any one of the names shown in the following table:

  • RESERVED: Reserved by the system; cannot be overridden.

  • DISK_OPERATIONS: If a log file group is allocated, the size of the undo log buffer is used to set the size of this resource. This resource is used only to allocate the undo log buffer for an undo log file group; there can only be one such group. Overallocation occurs as needed by CREATE LOGFILE GROUP.

  • DISK_RECORDS: Records allocated for Disk Data operations.

  • DATA_MEMORY: Used for main memory tuples, indexes, and hash indexes. Sum of DataMemory and IndexMemory, plus 8 pages of 32 KB each if IndexMemory has been set. Cannot be overallocated.

  • JOBBUFFER: Used for allocating job buffers by the NDB scheduler; cannot be overallocated. This is approximately 2 MB per thread plus a 1 MB buffer in both directions for all threads that can communicate. For large configurations this consume several GB.

  • FILE_BUFFERS: Used by the redo log handler in the DBLQH kernel block; cannot be overallocated. Size is NoOfFragmentLogParts * RedoBuffer, plus 1 MB per log file part.

  • TRANSPORTER_BUFFERS: Used for send buffers by ndbmtd; the sum of TotalSendBufferMemory and ExtraSendBufferMemory. This resource that can be overallocated by up to 25 percent. TotalSendBufferMemory is calculated by summing the send buffer memory per node, the default value of which is 2 MB. Thus, in a system having four data nodes and eight API nodes, the data nodes have 12 * 2 MB send buffer memory. ExtraSendBufferMemory is used by ndbmtd and amounts to 2 MB extra memory per thread. Thus, with 4 LDM threads, 2 TC threads, 1 main thread, 1 replication thread, and 2 receive threads, ExtraSendBufferMemory is 10 * 2 MB. Overallocation of this resource can be performed by setting the SharedGlobalMemory data node configuration parameter.

  • DISK_PAGE_BUFFER: Used for the disk page buffer; determined by the DiskPageBufferMemory configuration parameter. Cannot be overallocated.

  • QUERY_MEMORY: Used by the DBSPJ kernel block.

  • SCHEMA_TRANS_MEMORY: Minimum is 2 MB; can be overallocated to use any remaining available memory.

23.5.14.43 The ndbinfo restart_info Table

The restart_info table contains information about node restart operations. Each entry in the table corresponds to a node restart status report in real time from a data node with the given node ID. Only the most recent report for any given node is shown.

The restart_info table contains the following columns:

  • node_id

    Node ID in the cluster

  • node_restart_status

    Node status; see text for values. Each of these corresponds to a possible value of node_restart_status_int.

  • node_restart_status_int

    Node status code; see text for values.

  • secs_to_complete_node_failure

    Time in seconds to complete node failure handling

  • secs_to_allocate_node_id

    Time in seconds from node failure completion to allocation of node ID

  • secs_to_include_in_heartbeat_protocol

    Time in seconds from allocation of node ID to inclusion in heartbeat protocol

  • secs_until_wait_for_ndbcntr_master

    Time in seconds from being included in heartbeat protocol until waiting for NDBCNTR master began

  • secs_wait_for_ndbcntr_master

    Time in seconds spent waiting to be accepted by NDBCNTR master for starting

  • secs_to_get_start_permitted

    Time in seconds elapsed from receiving of permission for start from master until all nodes have accepted start of this node

  • secs_to_wait_for_lcp_for_copy_meta_data

    Time in seconds spent waiting for LCP completion before copying metadata

  • secs_to_copy_meta_data

    Time in seconds required to copy metadata from master to newly starting node

  • secs_to_include_node

    Time in seconds waited for GCP and inclusion of all nodes into protocols

  • secs_starting_node_to_request_local_recovery

    Time in seconds that the node just starting spent waiting to request local recovery

  • secs_for_local_recovery

    Time in seconds required for local recovery by node just starting

  • secs_restore_fragments

    Time in seconds required to restore fragments from LCP files

  • secs_undo_disk_data

    Time in seconds required to execute undo log on disk data part of records

  • secs_exec_redo_log

    Time in seconds required to execute redo log on all restored fragments

  • secs_index_rebuild

    Time in seconds required to rebuild indexes on restored fragments

  • secs_to_synchronize_starting_node

    Time in seconds required to synchronize starting node from live nodes

  • secs_wait_lcp_for_restart

    Time in seconds required for LCP start and completion before restart was completed

  • secs_wait_subscription_handover

    Time in seconds spent waiting for handover of replication subscriptions

  • total_restart_secs

    Total number of seconds from node failure until node is started again

Notes

The following list contains values defined for the node_restart_status_int column with their internal status names (in parentheses), and the corresponding messages shown in the node_restart_status column:

  • 0 (ALLOCATED_NODE_ID)

    Allocated node id

  • 1 (INCLUDED_IN_HB_PROTOCOL)

    Included in heartbeat protocol

  • 2 (NDBCNTR_START_WAIT)

    Wait for NDBCNTR master to permit us to start

  • 3 (NDBCNTR_STARTED)

    NDBCNTR master permitted us to start

  • 4 (START_PERMITTED)

    All nodes permitted us to start

  • 5 (WAIT_LCP_TO_COPY_DICT)

    Wait for LCP completion to start copying metadata

  • 6 (COPY_DICT_TO_STARTING_NODE)

    Copying metadata to starting node

  • 7 (INCLUDE_NODE_IN_LCP_AND_GCP)

    Include node in LCP and GCP protocols

  • 8 (LOCAL_RECOVERY_STARTED)

    Restore fragments ongoing

  • 9 (COPY_FRAGMENTS_STARTED)

    Synchronizing starting node with live nodes

  • 10 (WAIT_LCP_FOR_RESTART)

    Wait for LCP to ensure durability

  • 11 (WAIT_SUMA_HANDOVER)

    Wait for handover of subscriptions

  • 12 (RESTART_COMPLETED)

    Restart completed

  • 13 (NODE_FAILED)

    Node failed, failure handling in progress

  • 14 (NODE_FAILURE_COMPLETED)

    Node failure handling completed

  • 15 (NODE_GETTING_PERMIT)

    All nodes permitted us to start

  • 16 (NODE_GETTING_INCLUDED)

    Include node in LCP and GCP protocols

  • 17 (NODE_GETTING_SYNCHED)

    Synchronizing starting node with live nodes

  • 18 (NODE_GETTING_LCP_WAITED)

    [none]

  • 19 (NODE_ACTIVE)

    Restart completed

  • 20 (NOT_DEFINED_IN_CLUSTER)

    [none]

  • 21 (NODE_NOT_RESTARTED_YET)

    Initial state

Status numbers 0 through 12 apply on master nodes only; the remainder of those shown in the table apply to all restarting data nodes. Status numbers 13 and 14 define node failure states; 20 and 21 occur when no information about the restart of a given node is available.

See also Section 23.5.4, “Summary of NDB Cluster Start Phases”.

23.5.14.44 The ndbinfo server_locks Table

The server_locks table is similar in structure to the cluster_locks table, and provides a subset of the information found in the latter table, but which is specific to the SQL node (MySQL server) where it resides. (The cluster_locks table provides information about all locks in the cluster.) More precisely, server_locks contains information about locks requested by threads belonging to the current mysqld instance, and serves as a companion table to server_operations. This may be useful for correlating locking patterns with specific MySQL user sessions, queries, or use cases.

The server_locks table contains the following columns:

  • mysql_connection_id

    MySQL connection ID

  • node_id

    ID of reporting node

  • block_instance

    ID of reporting LDM instance

  • tableid

    ID of table containing this row

  • fragmentid

    ID of fragment containing locked row

  • rowid

    ID of locked row

  • transid

    Transaction ID

  • mode

    Lock request mode

  • state

    Lock state

  • detail

    Whether this is first holding lock in row lock queue

  • op

    Operation type

  • duration_millis

    Milliseconds spent waiting or holding lock

  • lock_num

    ID of lock object

  • waiting_for

    Waiting for lock with this ID

Notes

The mysql_connection_id column shows the MySQL connection or thread ID as shown by SHOW PROCESSLIST.

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table.

The tableid is assigned to the table by NDB; the same ID is used for this table in other ndbinfo tables, as well as in the output of ndb_show_tables.

The transaction ID shown in the transid column is the identifier generated by the NDB API for the transaction requesting or holding the current lock.

The mode column shows the lock mode, which is always one of S (shared lock) or X (exclusive lock). If a transaction has an exclusive lock on a given row, all other locks on that row have the same transaction ID.

The state column shows the lock state. Its value is always one of H (holding) or W (waiting). A waiting lock request waits for a lock held by a different transaction.

The detail column indicates whether this lock is the first holding lock in the affected row's lock queue, in which case it contains a * (asterisk character); otherwise, this column is empty. This information can be used to help identify the unique entries in a list of lock requests.

The op column shows the type of operation requesting the lock. This is always one of the values READ, INSERT, UPDATE, DELETE, SCAN, or REFRESH.

The duration_millis column shows the number of milliseconds for which this lock request has been waiting or holding the lock. This is reset to 0 when a lock is granted for a waiting request.

The lock ID (lockid column) is unique to this node and block instance.

If the lock_state column's value is W, this lock is waiting to be granted, and the waiting_for column shows the lock ID of the lock object this request is waiting for. Otherwise, waiting_for is empty. waiting_for can refer only to locks on the same row (as identified by node_id, block_instance, tableid, fragmentid, and rowid).

23.5.14.45 The ndbinfo server_operations Table

The server_operations table contains entries for all ongoing NDB operations that the current SQL node (MySQL Server) is currently involved in. It effectively is a subset of the cluster_operations table, in which operations for other SQL and API nodes are not shown.

The server_operations table contains the following columns:

  • mysql_connection_id

    MySQL Server connection ID

  • node_id

    Node ID

  • block_instance

    Block instance

  • transid

    Transaction ID

  • operation_type

    Operation type (see text for possible values)

  • state

    Operation state (see text for possible values)

  • tableid

    Table ID

  • fragmentid

    Fragment ID

  • client_node_id

    Client node ID

  • client_block_ref

    Client block reference

  • tc_node_id

    Transaction coordinator node ID

  • tc_block_no

    Transaction coordinator block number

  • tc_block_instance

    Transaction coordinator block instance

Notes

The mysql_connection_id is the same as the connection or session ID shown in the output of SHOW PROCESSLIST. It is obtained from the INFORMATION_SCHEMA table NDB_TRANSID_MYSQL_CONNECTION_MAP.

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table.

The transaction ID (transid) is a unique 64-bit number which can be obtained using the NDB API's getTransactionId() method. (Currently, the MySQL Server does not expose the NDB API transaction ID of an ongoing transaction.)

The operation_type column can take any one of the values READ, READ-SH, READ-EX, INSERT, UPDATE, DELETE, WRITE, UNLOCK, REFRESH, SCAN, SCAN-SH, SCAN-EX, or <unknown>.

The state column can have any one of the values ABORT_QUEUED, ABORT_STOPPED, COMMITTED, COMMIT_QUEUED, COMMIT_STOPPED, COPY_CLOSE_STOPPED, COPY_FIRST_STOPPED, COPY_STOPPED, COPY_TUPKEY, IDLE, LOG_ABORT_QUEUED, LOG_COMMIT_QUEUED, LOG_COMMIT_QUEUED_WAIT_SIGNAL, LOG_COMMIT_WRITTEN, LOG_COMMIT_WRITTEN_WAIT_SIGNAL, LOG_QUEUED, PREPARED, PREPARED_RECEIVED_COMMIT, SCAN_CHECK_STOPPED, SCAN_CLOSE_STOPPED, SCAN_FIRST_STOPPED, SCAN_RELEASE_STOPPED, SCAN_STATE_USED, SCAN_STOPPED, SCAN_TUPKEY, STOPPED, TC_NOT_CONNECTED, WAIT_ACC, WAIT_ACC_ABORT, WAIT_AI_AFTER_ABORT, WAIT_ATTR, WAIT_SCAN_AI, WAIT_TUP, WAIT_TUPKEYINFO, WAIT_TUP_COMMIT, or WAIT_TUP_TO_ABORT. (If the MySQL Server is running with ndbinfo_show_hidden enabled, you can view this list of states by selecting from the ndb$dblqh_tcconnect_state table, which is normally hidden.)

You can obtain the name of an NDB table from its table ID by checking the output of ndb_show_tables.

The fragid is the same as the partition number seen in the output of ndb_desc --extra-partition-info (short form -p).

In client_node_id and client_block_ref, client refers to an NDB Cluster API or SQL node (that is, an NDB API client or a MySQL Server attached to the cluster).

The block_instance and tc_block_instance column provide NDB kernel block instance numbers. You can use these to obtain information about specific threads from the threadblocks table.

23.5.14.46 The ndbinfo server_transactions Table

The server_transactions table is subset of the cluster_transactions table, but includes only those transactions in which the current SQL node (MySQL Server) is a participant, while including the relevant connection IDs.

The server_transactions table contains the following columns:

  • mysql_connection_id

    MySQL Server connection ID

  • node_id

    Transaction coordinator node ID

  • block_instance

    Transaction coordinator block instance

  • transid

    Transaction ID

  • state

    Operation state (see text for possible values)

  • count_operations

    Number of stateful operations in the transaction

  • outstanding_operations

    Operations still being executed by local data management layer (LQH blocks)

  • inactive_seconds

    Time spent waiting for API

  • client_node_id

    Client node ID

  • client_block_ref

    Client block reference

Notes

The mysql_connection_id is the same as the connection or session ID shown in the output of SHOW PROCESSLIST. It is obtained from the INFORMATION_SCHEMA table NDB_TRANSID_MYSQL_CONNECTION_MAP.

block_instance refers to an instance of a kernel block. Together with the block name, this number can be used to look up a given instance in the threadblocks table.

The transaction ID (transid) is a unique 64-bit number which can be obtained using the NDB API's getTransactionId() method. (Currently, the MySQL Server does not expose the NDB API transaction ID of an ongoing transaction.)

The state column can have any one of the values CS_ABORTING, CS_COMMITTING, CS_COMMIT_SENT, CS_COMPLETE_SENT, CS_COMPLETING, CS_CONNECTED, CS_DISCONNECTED, CS_FAIL_ABORTED, CS_FAIL_ABORTING, CS_FAIL_COMMITTED, CS_FAIL_COMMITTING, CS_FAIL_COMPLETED, CS_FAIL_PREPARED, CS_PREPARE_TO_COMMIT, CS_RECEIVING, CS_REC_COMMITTING, CS_RESTART, CS_SEND_FIRE_TRIG_REQ, CS_STARTED, CS_START_COMMITTING, CS_START_SCAN, CS_WAIT_ABORT_CONF, CS_WAIT_COMMIT_CONF, CS_WAIT_COMPLETE_CONF, CS_WAIT_FIRE_TRIG_REQ. (If the MySQL Server is running with ndbinfo_show_hidden enabled, you can view this list of states by selecting from the ndb$dbtc_apiconnect_state table, which is normally hidden.)

In client_node_id and client_block_ref, client refers to an NDB Cluster API or SQL node (that is, an NDB API client or a MySQL Server attached to the cluster).

The block_instance column provides the DBTC kernel block instance number. You can use this to obtain information about specific threads from the threadblocks table.

23.5.14.47 The ndbinfo table_distribution_status Table

The table_distribution_status table provides information about the progress of table distribution for NDB tables.

The table_distribution_status table contains the following columns:

  • node_id

    Node id

  • table_id

    Table ID

  • tab_copy_status

    Status of copying of table distribution data to disk; one of IDLE, SR_PHASE1_READ_PAGES, SR_PHASE2_READ_TABLE, SR_PHASE3_COPY_TABLE, REMOVE_NODE, LCP_READ_TABLE, COPY_TAB_REQ, COPY_NODE_STATE, ADD_TABLE_COORDINATOR (prior to NDB 8.0.23: ADD_TABLE_MASTER), ADD_TABLE_PARTICIPANT (prior to NDB 8.0.23: ADD_TABLE_SLAVE), INVALIDATE_NODE_LCP, ALTER_TABLE, COPY_TO_SAVE, or GET_TABINFO

  • tab_update_status

    Status of updating of table distribution data; one of IDLE, LOCAL_CHECKPOINT, LOCAL_CHECKPOINT_QUEUED, REMOVE_NODE, COPY_TAB_REQ, ADD_TABLE_MASTER, ADD_TABLE_SLAVE, INVALIDATE_NODE_LCP, or CALLBACK

  • tab_lcp_status

    Status of table LCP; one of ACTIVE (waiting for local checkpoint to be performed), WRITING_TO_FILE (checkpoint performed but not yet written to disk), or COMPLETED (checkpoint performed and persisted to disk)

  • tab_status

    Table internal status; one of ACTIVE (table exists), CREATING (table is being created), or DROPPING (table is being dropped)

  • tab_storage

    Table recoverability; one of NORMAL (fully recoverable with redo logging and checkpointing), NOLOGGING (recoverable from node crash, empty following cluster crash), or TEMPORARY (not recoverable)

  • tab_partitions

    Number of partitions in table

  • tab_fragments

    Number of fragments in table; normally same as tab_partitions; for fully replicated tables equal to tab_partitions * [number of node groups]

  • current_scan_count

    Current number of active scans

  • scan_count_wait

    Current number of scans waiting to be performed before ALTER TABLE can complete.

  • is_reorg_ongoing

    Whether the table is currently being reorganized (1 if true)

23.5.14.48 The ndbinfo table_fragments Table

The table_fragments table provides information about the fragmentation, partitioning, distribution, and (internal) replication of NDB tables.

The table_fragments table contains the following columns:

  • node_id

    Node ID (DIH master)

  • table_id

    Table ID

  • partition_id

    Partition ID

  • fragment_id

    Fragment ID (same as partition ID unless table is fully replicated)

  • partition_order

    Order of fragment in partition

  • log_part_id

    Log part ID of fragment

  • no_of_replicas

    Number of fragment replicas

  • current_primary

    Current primary node ID

  • preferred_primary

    Preferred primary node ID

  • current_first_backup

    Current first backup node ID

  • current_second_backup

    Current second backup node ID

  • current_third_backup

    Current third backup node ID

  • num_alive_replicas

    Current number of live fragment replicas

  • num_dead_replicas

    Current number of dead fragment replicas

  • num_lcp_replicas

    Number of fragment replicas remaining to be checkpointed

23.5.14.49 The ndbinfo table_info Table

The table_info table provides information about logging, checkpointing, distribution, and storage options in effect for individual NDB tables.

The table_info table contains the following columns:

  • table_id

    Table ID

  • logged_table

    Whether table is logged (1) or not (0)

  • row_contains_gci

    Whether table rows contain GCI (1 true, 0 false)

  • row_contains_checksum

    Whether table rows contain checksum (1 true, 0 false)

  • read_backup

    If backup fragment replicas are read this is 1, otherwise 0

  • fully_replicated

    If table is fully replicated this is 1, otherwise 0

  • storage_type

    Table storage type; one of MEMORY or DISK

  • hashmap_id

    Hashmap ID

  • partition_balance

    Partition balance (fragment count type) used for table; one of FOR_RP_BY_NODE, FOR_RA_BY_NODE, FOR_RP_BY_LDM, or FOR_RA_BY_LDM

  • create_gci

    GCI in which table was created

23.5.14.50 The ndbinfo table_replicas Table

The table_replicas table provides information about the copying, distribution, and checkpointing of NDB table fragments and fragment replicas.

The table_replicas table contains the following columns:

  • node_id

    ID of the node from which data is fetched (DIH master)

  • table_id

    Table ID

  • fragment_id

    Fragment ID

  • initial_gci

    Initial GCI for table

  • replica_node_id

    ID of node where fragment replica is stored

  • is_lcp_ongoing

    Is 1 if LCP is ongoing on this fragment, 0 otherwise

  • num_crashed_replicas

    Number of crashed fragment replica instances

  • last_max_gci_started

    Highest GCI started in most recent LCP

  • last_max_gci_completed

    Highest GCI completed in most recent LCP

  • last_lcp_id

    ID of most recent LCP

  • prev_lcp_id

    ID of previous LCP

  • prev_max_gci_started

    Highest GCI started in previous LCP

  • prev_max_gci_completed

    Highest GCI completed in previous LCP

  • last_create_gci

    Last Create GCI of last crashed fragment replica instance

  • last_replica_gci

    Last GCI of last crashed fragment replica instance

  • is_replica_alive

    1 if this fragment replica is alive, 0 otherwise

23.5.14.51 The ndbinfo tc_time_track_stats Table

The tc_time_track_stats table provides time-tracking information obtained from the DBTC block (TC) instances in the data nodes, through API nodes access NDB. Each TC instance tracks latencies for a set of activities it undertakes on behalf of API nodes or other data nodes; these activities include transactions, transaction errors, key reads, key writes, unique index operations, failed key operations of any type, scans, failed scans, fragment scans, and failed fragment scans.

A set of counters is maintained for each activity, each counter covering a range of latencies less than or equal to an upper bound. At the conclusion of each activity, its latency is determined and the appropriate counter incremented. tc_time_track_stats presents this information as rows, with a row for each instance of the following:

  • Data node, using its ID

  • TC block instance

  • Other communicating data node or API node, using its ID

  • Upper bound value

Each row contains a value for each activity type. This is the number of times that this activity occurred with a latency within the range specified by the row (that is, where the latency does not exceed the upper bound).

The tc_time_track_stats table contains the following columns:

  • node_id

    Requesting node ID

  • block_number

    TC block number

  • block_instance

    TC block instance number

  • comm_node_id

    Node ID of communicating API or data node

  • upper_bound

    Upper bound of interval (in microseconds)

  • scans

    Based on duration of successful scans from opening to closing, tracked against the API or data nodes requesting them.

  • scan_errors

    Based on duration of failed scans from opening to closing, tracked against the API or data nodes requesting them.

  • scan_fragments

    Based on duration of successful fragment scans from opening to closing, tracked against the data nodes executing them

  • scan_fragment_errors

    Based on duration of failed fragment scans from opening to closing, tracked against the data nodes executing them

  • transactions

    Based on duration of successful transactions from beginning until sending of commit ACK, tracked against the API or data nodes requesting them. Stateless transactions are not included.

  • transaction_errors

    Based on duration of failing transactions from start to point of failure, tracked against the API or data nodes requesting them.

  • read_key_ops

    Based on duration of successful primary key reads with locks. Tracked against both the API or data node requesting them and the data node executing them.

  • write_key_ops

    Based on duration of successful primary key writes, tracked against both the API or data node requesting them and the data node executing them.

  • index_key_ops

    Based on duration of successful unique index key operations, tracked against both the API or data node requesting them and the data node executing reads of base tables.

  • key_op_errors

    Based on duration of all unsuccessful key read or write operations, tracked against both the API or data node requesting them and the data node executing them.

Notes

The block_instance column provides the DBTC kernel block instance number. You can use this together with the block name to obtain information about specific threads from the threadblocks table.

23.5.14.52 The ndbinfo threadblocks Table

The threadblocks table associates data nodes, threads, and instances of NDB kernel blocks.

The threadblocks table contains the following columns:

  • node_id

    Node ID

  • thr_no

    Thread ID

  • block_name

    Block name

  • block_instance

    Block instance number

Notes

The value of the block_name in this table is one of the values found in the block_name column when selecting from the ndbinfo.blocks table. Although the list of possible values is static for a given NDB Cluster release, the list may vary between releases.

The block_instance column provides the kernel block instance number.

23.5.14.53 The ndbinfo threads Table

The threads table provides information about threads running in the NDB kernel.

The threads table contains the following columns:

  • node_id

    ID of the node where the thread is running

  • thr_no

    Thread ID (specific to this node)

  • thread_name

    Thread name (type of thread)

  • thread_description

    Thread (type) description

Notes

Sample output from a 2-node example cluster, including thread descriptions, is shown here:

mysql> SELECT * FROM threads;
+---------+--------+-------------+------------------------------------------------------------------+
| node_id | thr_no | thread_name | thread_description                                               |
+---------+--------+-------------+------------------------------------------------------------------+
|       5 |      0 | main        | main thread, schema and distribution handling                    |
|       5 |      1 | rep         | rep thread, asynch replication and proxy block handling          |
|       5 |      2 | ldm         | ldm thread, handling a set of data partitions                    |
|       5 |      3 | recv        | receive thread, performing receive and polling for new receives  |
|       6 |      0 | main        | main thread, schema and distribution handling                    |
|       6 |      1 | rep         | rep thread, asynch replication and proxy block handling          |
|       6 |      2 | ldm         | ldm thread, handling a set of data partitions                    |
|       6 |      3 | recv        | receive thread, performing receive and polling for new receives  |
+---------+--------+-------------+------------------------------------------------------------------+
8 rows in set (0.01 sec)

NDB 8.0.23 introduces the possibility to set either of the ThreadConfig arguments main or rep to 0 while keeping the other at 1, in which case the thread name is main_rep and its description is main and rep thread, schema, distribution, proxy block and asynch replication handling. It is also possible beginning with NDB 8.0.23 to set both main and rep to 0, in which case the name of the resulting thread is shown in this table as main_rep_recv, and its description is main, rep and recv thread, schema, distribution, proxy block and asynch replication handling and handling receive and polling for new receives.

23.5.14.54 The ndbinfo threadstat Table

The threadstat table provides a rough snapshot of statistics for threads running in the NDB kernel.

The threadstat table contains the following columns:

  • node_id

    Node ID

  • thr_no

    Thread ID

  • thr_nm

    Thread name

  • c_loop

    Number of loops in main loop

  • c_exec

    Number of signals executed

  • c_wait

    Number of times waiting for additional input

  • c_l_sent_prioa

    Number of priority A signals sent to own node

  • c_l_sent_priob

    Number of priority B signals sent to own node

  • c_r_sent_prioa

    Number of priority A signals sent to remote node

  • c_r_sent_priob

    Number of priority B signals sent to remote node

  • os_tid

    OS thread ID

  • os_now

    OS time (ms)

  • os_ru_utime

    OS user CPU time (µs)

  • os_ru_stime

    OS system CPU time (µs)

  • os_ru_minflt

    OS page reclaims (soft page faults)

  • os_ru_majflt

    OS page faults (hard page faults)

  • os_ru_nvcsw

    OS voluntary context switches

  • os_ru_nivcsw

    OS involuntary context switches

Notes

os_time uses the system gettimeofday() call.

The values of the os_ru_utime, os_ru_stime, os_ru_minflt, os_ru_majflt, os_ru_nvcsw, and os_ru_nivcsw columns are obtained using the system getrusage() call, or the equivalent.

Since this table contains counts taken at a given point in time, for best results it is necessary to query this table periodically and store the results in an intermediate table or tables. The MySQL Server's Event Scheduler can be employed to automate such monitoring. For more information, see Section 25.4, “Using the Event Scheduler”.

23.5.14.55 The ndbinfo transporters Table

This table contains information about NDB transporters.

The transporters table contains the following columns:

  • node_id

    This data node's unique node ID in the cluster

  • remote_node_id

    The remote data node's node ID

  • status

    Status of the connection

  • remote_address

    Name or IP address of the remote host

  • bytes_sent

    Number of bytes sent using this connection

  • bytes_received

    Number of bytes received using this connection

  • connect_count

    Number of times connection established on this transporter

  • overloaded

    1 if this transporter is currently overloaded, otherwise 0

  • overload_count

    Number of times this transporter has entered overload state since connecting

  • slowdown

    1 if this transporter is in slowdown state, otherwise 0

  • slowdown_count

    Number of times this transporter has entered slowdown state since connecting

Notes

For each running data node in the cluster, the transporters table displays a row showing the status of each of that node's connections with all nodes in the cluster, including itself. This information is shown in the table's status column, which can have any one of the following values: CONNECTING, CONNECTED, DISCONNECTING, or DISCONNECTED.

Connections to API and management nodes which are configured but not currently connected to the cluster are shown with status DISCONNECTED. Rows where the node_id is that of a data node which is not currently connected are not shown in this table. (This is similar omission of disconnected nodes in the ndbinfo.nodes table.

The remote_address is the host name or address for the node whose ID is shown in the remote_node_id column. The bytes_sent from this node and bytes_received by this node are the numbers, respectively, of bytes sent and received by the node using this connection since it was established. For nodes whose status is CONNECTING or DISCONNECTED, these columns always display 0.

Assume you have a 5-node cluster consisting of 2 data nodes, 2 SQL nodes, and 1 management node, as shown in the output of the SHOW command in the ndb_mgm client:

ndb_mgm> SHOW
Connected to Management Server at: localhost:1186
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=1    @10.100.10.1  (8.0.23-ndb-8.0.23, Nodegroup: 0, *)
id=2    @10.100.10.2  (8.0.23-ndb-8.0.23, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=10   @10.100.10.10  (8.0.23-ndb-8.0.23)

[mysqld(API)]   2 node(s)
id=20   @10.100.10.20  (8.0.23-ndb-8.0.23)
id=21   @10.100.10.21  (8.0.23-ndb-8.0.23)

There are 10 rows in the transporters table—5 for the first data node, and 5 for the second—assuming that all data nodes are running, as shown here:

mysql> SELECT node_id, remote_node_id, status
    ->   FROM ndbinfo.transporters;
+---------+----------------+---------------+
| node_id | remote_node_id | status        |
+---------+----------------+---------------+
|       1 |              1 | DISCONNECTED  |
|       1 |              2 | CONNECTED     |
|       1 |             10 | CONNECTED     |
|       1 |             20 | CONNECTED     |
|       1 |             21 | CONNECTED     |
|       2 |              1 | CONNECTED     |
|       2 |              2 | DISCONNECTED  |
|       2 |             10 | CONNECTED     |
|       2 |             20 | CONNECTED     |
|       2 |             21 | CONNECTED     |
+---------+----------------+---------------+
10 rows in set (0.04 sec)

If you shut down one of the data nodes in this cluster using the command 2 STOP in the ndb_mgm client, then repeat the previous query (again using the mysql client), this table now shows only 5 rows—1 row for each connection from the remaining management node to another node, including both itself and the data node that is currently offline—and displays CONNECTING for the status of each remaining connection to the data node that is currently offline, as shown here:

mysql> SELECT node_id, remote_node_id, status
    ->   FROM ndbinfo.transporters;
+---------+----------------+---------------+
| node_id | remote_node_id | status        |
+---------+----------------+---------------+
|       1 |              1 | DISCONNECTED  |
|       1 |              2 | CONNECTING    |
|       1 |             10 | CONNECTED     |
|       1 |             20 | CONNECTED     |
|       1 |             21 | CONNECTED     |
+---------+----------------+---------------+
5 rows in set (0.02 sec)

The connect_count, overloaded, overload_count, slowdown, and slowdown_count counters are reset on connection, and retain their values after the remote node disconnects. The bytes_sent and bytes_received counters are also reset on connection, and so retain their values following disconnection (until the next connection resets them).

The overload state referred to by the overloaded and overload_count columns occurs when this transporter's send buffer contains more than OVerloadLimit bytes (default is 80% of SendBufferMemory, that is, 0.8 * 2097152 = 1677721 bytes). When a given transporter is in a state of overload, any new transaction that tries to use this transporter fails with Error 1218 (Send Buffers overloaded in NDB kernel). This affects both scans and primary key operations.

The slowdown state referenced by the slowdown and slowdown_count columns of this table occurs when the transporter's send buffer contains more than 60% of the overload limit (equal to 0.6 * 2097152 = 1258291 bytes by default). In this state, any new scan using this transporter has its batch size reduced to minimize the load on the transporter.

Common causes of send buffer slowdown or overloading include the following:

  • Data size, in particular the quantity of data stored in TEXT columns or BLOB columns (or both types of columns)

  • Having a data node (ndbd or ndbmtd) on the same host as an SQL node that is engaged in binary logging

  • Large number of rows per transaction or transaction batch

  • Configuration issues such as insufficient SendBufferMemory

  • Hardware issues such as insufficient RAM or poor network connectivity

See also Section 23.3.3.14, “Configuring NDB Cluster Send Buffer Parameters”.

23.5.15 INFORMATION_SCHEMA Tables for NDB Cluster

Two INFORMATION_SCHEMA tables provide information that is of particular use when managing an NDB Cluster. The FILES table provides information about NDB Cluster Disk Data files (see Section 23.5.10.1, “NDB Cluster Disk Data Objects”). The ndb_transid_mysql_connection_map table provides a mapping between transactions, transaction coordinators, and API nodes.

Additional statistical and other data about NDB Cluster transactions, operations, threads, blocks, and other aspects of performance can be obtained from the tables in the ndbinfo database. For information about these tables, see Section 23.5.14, “ndbinfo: The NDB Cluster Information Database”.

23.5.16 Quick Reference: NDB Cluster SQL Statements

This section discusses several SQL statements that can prove useful in managing and monitoring a MySQL server that is connected to an NDB Cluster, and in some cases provide information about the cluster itself.

  • SHOW ENGINE NDB STATUS, SHOW ENGINE NDBCLUSTER STATUS

    The output of this statement contains information about the server's connection to the cluster, creation and usage of NDB Cluster objects, and binary logging for NDB Cluster replication.

    See Section 13.7.7.15, “SHOW ENGINE Statement”, for a usage example and more detailed information.

  • SHOW ENGINES

    This statement can be used to determine whether or not clustering support is enabled in the MySQL server, and if so, whether it is active.

    See Section 13.7.7.16, “SHOW ENGINES Statement”, for more detailed information.

    Note

    This statement does not support a LIKE clause. However, you can use LIKE to filter queries against the INFORMATION_SCHEMA.ENGINES table, as discussed in the next item.

  • SELECT * FROM INFORMATION_SCHEMA.ENGINES [WHERE ENGINE LIKE 'NDB%']

    This is the equivalent of SHOW ENGINES, but uses the ENGINES table of the INFORMATION_SCHEMA database. Unlike the case with the SHOW ENGINES statement, it is possible to filter the results using a LIKE clause, and to select specific columns to obtain information that may be of use in scripts. For example, the following query shows whether the server was built with NDB support and, if so, whether it is enabled:

    mysql> SELECT ENGINE, SUPPORT FROM INFORMATION_SCHEMA.ENGINES
        ->   WHERE ENGINE LIKE 'NDB%';
    +------------+---------+
    | ENGINE     | SUPPORT |
    +------------+---------+
    | ndbcluster | YES     |
    | ndbinfo    | YES     |
    +------------+---------+
    

    If NDB support is not enabled, the preceding query returns an empty set. See Section 26.13, “The INFORMATION_SCHEMA ENGINES Table”, for more information.

  • SHOW VARIABLES LIKE 'NDB%'

    This statement provides a list of most server system variables relating to the NDB storage engine, and their values, as shown here:

    mysql> SHOW VARIABLES LIKE 'NDB%';
    +--------------------------------------+---------------------------------------+
    | Variable_name                        | Value                                 |
    +--------------------------------------+---------------------------------------+
    | ndb_allow_copying_alter_table        | ON                                    |
    | ndb_autoincrement_prefetch_sz        | 512                                   |
    | ndb_batch_size                       | 32768                                 |
    | ndb_blob_read_batch_bytes            | 65536                                 |
    | ndb_blob_write_batch_bytes           | 65536                                 |
    | ndb_clear_apply_status               | ON                                    |
    | ndb_cluster_connection_pool          | 1                                     |
    | ndb_cluster_connection_pool_nodeids  |                                       |
    | ndb_connectstring                    | 127.0.0.1                             |
    | ndb_data_node_neighbour              | 0                                     |
    | ndb_default_column_format            | FIXED                                 |
    | ndb_deferred_constraints             | 0                                     |
    | ndb_distribution                     | KEYHASH                               |
    | ndb_eventbuffer_free_percent         | 20                                    |
    | ndb_eventbuffer_max_alloc            | 0                                     |
    | ndb_extra_logging                    | 1                                     |
    | ndb_force_send                       | ON                                    |
    | ndb_fully_replicated                 | OFF                                   |
    | ndb_index_stat_enable                | ON                                    |
    | ndb_index_stat_option                | loop_enable=1000ms,loop_idle=1000ms,
    loop_busy=100ms,update_batch=1,read_batch=4,idle_batch=32,check_batch=8,
    check_delay=10m,delete_batch=8,clean_delay=1m,error_batch=4,error_delay=1m,
    evict_batch=8,evict_delay=1m,cache_limit=32M,cache_lowpct=90,zero_total=0      |
    | ndb_join_pushdown                    | ON                                    |
    | ndb_log_apply_status                 | OFF                                   |
    | ndb_log_bin                          | OFF                                   |
    | ndb_log_binlog_index                 | ON                                    |
    | ndb_log_empty_epochs                 | OFF                                   |
    | ndb_log_empty_update                 | OFF                                   |
    | ndb_log_exclusive_reads              | OFF                                   |
    | ndb_log_orig                         | OFF                                   |
    | ndb_log_transaction_id               | OFF                                   |
    | ndb_log_update_as_write              | ON                                    |
    | ndb_log_update_minimal               | OFF                                   |
    | ndb_log_updated_only                 | ON                                    |
    | ndb_metadata_check                   | ON                                    |
    | ndb_metadata_check_interval          | 60                                    |
    | ndb_metadata_sync                    | OFF                                   |
    | ndb_mgmd_host                        | 127.0.0.1                             |
    | ndb_nodeid                           | 0                                     |
    | ndb_optimization_delay               | 10                                    |
    | ndb_optimized_node_selection         | 3                                     |
    | ndb_read_backup                      | ON                                    |
    | ndb_recv_thread_activation_threshold | 8                                     |
    | ndb_recv_thread_cpu_mask             |                                       |
    | ndb_report_thresh_binlog_epoch_slip  | 10                                    |
    | ndb_report_thresh_binlog_mem_usage   | 10                                    |
    | ndb_row_checksum                     | 1                                     |
    | ndb_schema_dist_lock_wait_timeout    | 30                                    |
    | ndb_schema_dist_timeout              | 120                                   |
    | ndb_schema_dist_upgrade_allowed      | ON                                    |
    | ndb_show_foreign_key_mock_tables     | OFF                                   |
    | ndb_slave_conflict_role              | NONE                                  |
    | ndb_table_no_logging                 | OFF                                   |
    | ndb_table_temporary                  | OFF                                   |
    | ndb_use_copying_alter_table          | OFF                                   |
    | ndb_use_exact_count                  | OFF                                   |
    | ndb_use_transactions                 | ON                                    |
    | ndb_version                          | 524308                                |
    | ndb_version_string                   | ndb-8.0.23                            |
    | ndb_wait_connected                   | 30                                    |
    | ndb_wait_setup                       | 30                                    |
    | ndbinfo_database                     | ndbinfo                               |
    | ndbinfo_max_bytes                    | 0                                     |
    | ndbinfo_max_rows                     | 10                                    |
    | ndbinfo_offline                      | OFF                                   |
    | ndbinfo_show_hidden                  | OFF                                   |
    | ndbinfo_table_prefix                 | ndb$                                  |
    | ndbinfo_version                      | 524308                                |
    +--------------------------------------+---------------------------------------+
    

    See Section 5.1.8, “Server System Variables”, for more information.

  • SELECT * FROM performance_schema.global_variables WHERE VARIABLE_NAME LIKE 'NDB%'

    This statement is the equivalent of the SHOW VARIABLES statement described in the previous item, and provides almost identical output, as shown here:

    mysql> SELECT * FROM performance_schema.global_variables
        ->   WHERE VARIABLE_NAME LIKE 'NDB%';
    +--------------------------------------+---------------------------------------+
    | VARIABLE_NAME                        | VARIABLE_VALUE                        |
    +--------------------------------------+---------------------------------------+
    | ndb_allow_copying_alter_table        | ON                                    |
    | ndb_autoincrement_prefetch_sz        | 512                                   |
    | ndb_batch_size                       | 32768                                 |
    | ndb_blob_read_batch_bytes            | 65536                                 |
    | ndb_blob_write_batch_bytes           | 65536                                 |
    | ndb_clear_apply_status               | ON                                    |
    | ndb_cluster_connection_pool          | 1                                     |
    | ndb_cluster_connection_pool_nodeids  |                                       |
    | ndb_connectstring                    | 127.0.0.1                             |
    | ndb_data_node_neighbour              | 0                                     |
    | ndb_default_column_format            | FIXED                                 |
    | ndb_deferred_constraints             | 0                                     |
    | ndb_distribution                     | KEYHASH                               |
    | ndb_eventbuffer_free_percent         | 20                                    |
    | ndb_eventbuffer_max_alloc            | 0                                     |
    | ndb_extra_logging                    | 1                                     |
    | ndb_force_send                       | ON                                    |
    | ndb_fully_replicated                 | OFF                                   |
    | ndb_index_stat_enable                | ON                                    |
    | ndb_index_stat_option                | loop_enable=1000ms,loop_idle=1000ms,
    loop_busy=100ms,update_batch=1,read_batch=4,idle_batch=32,check_batch=8,
    check_delay=10m,delete_batch=8,clean_delay=1m,error_batch=4,error_delay=1m,
    evict_batch=8,evict_delay=1m,cache_limit=32M,cache_lowpct=90,zero_total=0      |
    | ndb_join_pushdown                    | ON                                    |
    | ndb_log_apply_status                 | OFF                                   |
    | ndb_log_bin                          | OFF                                   |
    | ndb_log_binlog_index                 | ON                                    |
    | ndb_log_empty_epochs                 | OFF                                   |
    | ndb_log_empty_update                 | OFF                                   |
    | ndb_log_exclusive_reads              | OFF                                   |
    | ndb_log_orig                         | OFF                                   |
    | ndb_log_transaction_id               | OFF                                   |
    | ndb_log_update_as_write              | ON                                    |
    | ndb_log_update_minimal               | OFF                                   |
    | ndb_log_updated_only                 | ON                                    |
    | ndb_metadata_check                   | ON                                    |
    | ndb_metadata_check_interval          | 60                                    |
    | ndb_metadata_sync                    | OFF                                   |
    | ndb_mgmd_host                        | 127.0.0.1                             |
    | ndb_nodeid                           | 0                                     |
    | ndb_optimization_delay               | 10                                    |
    | ndb_optimized_node_selection         | 3                                     |
    | ndb_read_backup                      | ON                                    |
    | ndb_recv_thread_activation_threshold | 8                                     |
    | ndb_recv_thread_cpu_mask             |                                       |
    | ndb_report_thresh_binlog_epoch_slip  | 10                                    |
    | ndb_report_thresh_binlog_mem_usage   | 10                                    |
    | ndb_row_checksum                     | 1                                     |
    | ndb_schema_dist_lock_wait_timeout    | 30                                    |
    | ndb_schema_dist_timeout              | 120                                   |
    | ndb_schema_dist_upgrade_allowed      | ON                                    |
    | ndb_show_foreign_key_mock_tables     | OFF                                   |
    | ndb_slave_conflict_role              | NONE                                  |
    | ndb_table_no_logging                 | OFF                                   |
    | ndb_table_temporary                  | OFF                                   |
    | ndb_use_copying_alter_table          | OFF                                   |
    | ndb_use_exact_count                  | OFF                                   |
    | ndb_use_transactions                 | ON                                    |
    | ndb_version                          | 524308                                |
    | ndb_version_string                   | ndb-8.0.23                            |
    | ndb_wait_connected                   | 30                                    |
    | ndb_wait_setup                       | 30                                    |
    | ndbinfo_database                     | ndbinfo                               |
    | ndbinfo_max_bytes                    | 0                                     |
    | ndbinfo_max_rows                     | 10                                    |
    | ndbinfo_offline                      | OFF                                   |
    | ndbinfo_show_hidden                  | OFF                                   |
    | ndbinfo_table_prefix                 | ndb$                                  |
    | ndbinfo_version                      | 524308                                |
    +--------------------------------------+---------------------------------------+
    

    Unlike the case with the SHOW VARIABLES statement, it is possible to select individual columns. For example:

    mysql> SELECT VARIABLE_VALUE 
        ->   FROM performance_schema.global_variables
        ->   WHERE VARIABLE_NAME = 'ndb_force_send';
    +----------------+
    | VARIABLE_VALUE |
    +----------------+
    | ON             |
    +----------------+
    

    A more useful query is shown here:

    mysql> SELECT VARIABLE_NAME AS Name, VARIABLE_VALUE AS Value
         >   FROM performance_schema.global_variables
         >   WHERE VARIABLE_NAME
         >     IN ('version', 'ndb_version',
         >       'ndb_version_string', 'ndbinfo_version');
    
    +--------------------+----------------+
    | Name               | Value          |
    +--------------------+----------------+
    | ndb_version        | 524308         |
    | ndb_version_string | ndb-8.0.20     |
    | ndbinfo_version    | 524308         |
    | version            | 8.0.20-cluster |
    +--------------------+----------------+
    4 rows in set (0.00 sec)
    

    For more information, see Section 27.12.15, “Performance Schema Status Variable Tables”, and Section 5.1.8, “Server System Variables”.

  • SHOW STATUS LIKE 'NDB%'

    This statement shows at a glance whether or not the MySQL server is acting as a cluster SQL node, and if so, it provides the MySQL server's cluster node ID, the host name and port for the cluster management server to which it is connected, and the number of data nodes in the cluster, as shown here:

    mysql> SHOW STATUS LIKE 'NDB%';
    +----------------------------------------------+-------------------------------+
    | Variable_name                                | Value                         |
    +----------------------------------------------+-------------------------------+
    | Ndb_metadata_detected_count                  | 0                             |
    | Ndb_cluster_node_id                          | 100                           |
    | Ndb_config_from_host                         | 127.0.0.1                     |
    | Ndb_config_from_port                         | 1186                          |
    | Ndb_number_of_data_nodes                     | 2                             |
    | Ndb_number_of_ready_data_nodes               | 2                             |
    | Ndb_connect_count                            | 0                             |
    | Ndb_execute_count                            | 0                             |
    | Ndb_scan_count                               | 0                             |
    | Ndb_pruned_scan_count                        | 0                             |
    | Ndb_schema_locks_count                       | 0                             |
    | Ndb_api_wait_exec_complete_count_session     | 0                             |
    | Ndb_api_wait_scan_result_count_session       | 0                             |
    | Ndb_api_wait_meta_request_count_session      | 1                             |
    | Ndb_api_wait_nanos_count_session             | 163446                        |
    | Ndb_api_bytes_sent_count_session             | 60                            |
    | Ndb_api_bytes_received_count_session         | 28                            |
    | Ndb_api_trans_start_count_session            | 0                             |
    | Ndb_api_trans_commit_count_session           | 0                             |
    | Ndb_api_trans_abort_count_session            | 0                             |
    | Ndb_api_trans_close_count_session            | 0                             |
    | Ndb_api_pk_op_count_session                  | 0                             |
    | Ndb_api_uk_op_count_session                  | 0                             |
    | Ndb_api_table_scan_count_session             | 0                             |
    | Ndb_api_range_scan_count_session             | 0                             |
    | Ndb_api_pruned_scan_count_session            | 0                             |
    | Ndb_api_scan_batch_count_session             | 0                             |
    | Ndb_api_read_row_count_session               | 0                             |
    | Ndb_api_trans_local_read_row_count_session   | 0                             |
    | Ndb_api_adaptive_send_forced_count_session   | 0                             |
    | Ndb_api_adaptive_send_unforced_count_session | 0                             |
    | Ndb_api_adaptive_send_deferred_count_session | 0                             |
    | Ndb_trans_hint_count_session                 | 0                             |
    | Ndb_sorted_scan_count                        | 0                             |
    | Ndb_pushed_queries_defined                   | 0                             |
    | Ndb_pushed_queries_dropped                   | 0                             |
    | Ndb_pushed_queries_executed                  | 0                             |
    | Ndb_pushed_reads                             | 0                             |
    | Ndb_last_commit_epoch_server                 | 37632503447571                |
    | Ndb_last_commit_epoch_session                | 0                             |
    | Ndb_system_name                              | MC_20191126162038             |
    | Ndb_api_event_data_count_injector            | 0                             |
    | Ndb_api_event_nondata_count_injector         | 0                             |
    | Ndb_api_event_bytes_count_injector           | 0                             |
    | Ndb_api_wait_exec_complete_count_slave       | 0                             |
    | Ndb_api_wait_scan_result_count_slave         | 0                             |
    | Ndb_api_wait_meta_request_count_slave        | 0                             |
    | Ndb_api_wait_nanos_count_slave               | 0                             |
    | Ndb_api_bytes_sent_count_slave               | 0                             |
    | Ndb_api_bytes_received_count_slave           | 0                             |
    | Ndb_api_trans_start_count_slave              | 0                             |
    | Ndb_api_trans_commit_count_slave             | 0                             |
    | Ndb_api_trans_abort_count_slave              | 0                             |
    | Ndb_api_trans_close_count_slave              | 0                             |
    | Ndb_api_pk_op_count_slave                    | 0                             |
    | Ndb_api_uk_op_count_slave                    | 0                             |
    | Ndb_api_table_scan_count_slave               | 0                             |
    | Ndb_api_range_scan_count_slave               | 0                             |
    | Ndb_api_pruned_scan_count_slave              | 0                             |
    | Ndb_api_scan_batch_count_slave               | 0                             |
    | Ndb_api_read_row_count_slave                 | 0                             |
    | Ndb_api_trans_local_read_row_count_slave     | 0                             |
    | Ndb_api_adaptive_send_forced_count_slave     | 0                             |
    | Ndb_api_adaptive_send_unforced_count_slave   | 0                             |
    | Ndb_api_adaptive_send_deferred_count_slave   | 0                             |
    | Ndb_slave_max_replicated_epoch               | 0                             |
    | Ndb_api_wait_exec_complete_count             | 4                             |
    | Ndb_api_wait_scan_result_count               | 7                             |
    | Ndb_api_wait_meta_request_count              | 172                           |
    | Ndb_api_wait_nanos_count                     | 1083548094028                 |
    | Ndb_api_bytes_sent_count                     | 4640                          |
    | Ndb_api_bytes_received_count                 | 109356                        |
    | Ndb_api_trans_start_count                    | 4                             |
    | Ndb_api_trans_commit_count                   | 1                             |
    | Ndb_api_trans_abort_count                    | 1                             |
    | Ndb_api_trans_close_count                    | 4                             |
    | Ndb_api_pk_op_count                          | 2                             |
    | Ndb_api_uk_op_count                          | 0                             |
    | Ndb_api_table_scan_count                     | 1                             |
    | Ndb_api_range_scan_count                     | 1                             |
    | Ndb_api_pruned_scan_count                    | 0                             |
    | Ndb_api_scan_batch_count                     | 1                             |
    | Ndb_api_read_row_count                       | 3                             |
    | Ndb_api_trans_local_read_row_count           | 2                             |
    | Ndb_api_adaptive_send_forced_count           | 1                             |
    | Ndb_api_adaptive_send_unforced_count         | 5                             |
    | Ndb_api_adaptive_send_deferred_count         | 0                             |
    | Ndb_api_event_data_count                     | 0                             |
    | Ndb_api_event_nondata_count                  | 0                             |
    | Ndb_api_event_bytes_count                    | 0                             |
    | Ndb_metadata_excluded_count                  | 0                             |
    | Ndb_metadata_synced_count                    | 0                             |
    | Ndb_conflict_fn_max                          | 0                             |
    | Ndb_conflict_fn_old                          | 0                             |
    | Ndb_conflict_fn_max_del_win                  | 0                             |
    | Ndb_conflict_fn_epoch                        | 0                             |
    | Ndb_conflict_fn_epoch_trans                  | 0                             |
    | Ndb_conflict_fn_epoch2                       | 0                             |
    | Ndb_conflict_fn_epoch2_trans                 | 0                             |
    | Ndb_conflict_trans_row_conflict_count        | 0                             |
    | Ndb_conflict_trans_row_reject_count          | 0                             |
    | Ndb_conflict_trans_reject_count              | 0                             |
    | Ndb_conflict_trans_detect_iter_count         | 0                             |
    | Ndb_conflict_trans_conflict_commit_count     | 0                             |
    | Ndb_conflict_epoch_delete_delete_count       | 0                             |
    | Ndb_conflict_reflected_op_prepare_count      | 0                             |
    | Ndb_conflict_reflected_op_discard_count      | 0                             |
    | Ndb_conflict_refresh_op_count                | 0                             |
    | Ndb_conflict_last_conflict_epoch             | 0                             |
    | Ndb_conflict_last_stable_epoch               | 0                             |
    | Ndb_index_stat_status                        | allow:1,enable:1,busy:0,
    loop:1000,list:(new:0,update:0,read:0,idle:0,check:0,delete:0,error:0,total:0),
    analyze:(queue:0,wait:0),stats:(nostats:0,wait:0),total:(analyze:(all:0,error:0),
    query:(all:0,nostats:0,error:0),event:(act:0,skip:0,miss:0),cache:(refresh:0,
    clean:0,pinned:0,drop:0,evict:0)),cache:(query:0,clean:0,drop:0,evict:0,
    usedpct:0.00,highpct:0.00)                                                     |
    | Ndb_index_stat_cache_query                   | 0                             |
    | Ndb_index_stat_cache_clean                   | 0                             |
    +----------------------------------------------+-------------------------------+
    

    If the MySQL server was built with NDB support, but it is not currently connected to a cluster, every row in the output of this statement contains a zero or an empty string for the Value column.

    See also Section 13.7.7.37, “SHOW STATUS Statement”.

  • SELECT * FROM performance_schema.global_status WHERE VARIABLE_NAME LIKE 'NDB%'

    This statement provides similar output to the SHOW STATUS statement discussed in the previous item. Unlike the case with SHOW STATUS, it is possible using SELECT statements to extract values in SQL for use in scripts for monitoring and automation purposes.

    For more information, see Section 27.12.15, “Performance Schema Status Variable Tables”.

  • SELECT * FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE 'NDB%'

    This statement displays information from the INFORMATION_SCHEMA.PLUGINS table about plugins associated with NDB Cluster, such as version, author, and license, as shown here:

    mysql> SELECT * FROM INFORMATION_SCHEMA.PLUGINS
         >     WHERE PLUGIN_NAME LIKE 'NDB%'\G
    *************************** 1. row ***************************
               PLUGIN_NAME: ndbcluster
            PLUGIN_VERSION: 1.0
             PLUGIN_STATUS: ACTIVE
               PLUGIN_TYPE: STORAGE ENGINE
       PLUGIN_TYPE_VERSION: 80024.0
            PLUGIN_LIBRARY: NULL
    PLUGIN_LIBRARY_VERSION: NULL
             PLUGIN_AUTHOR: Oracle Corporation
        PLUGIN_DESCRIPTION: Clustered, fault-tolerant tables
            PLUGIN_LICENSE: GPL
               LOAD_OPTION: ON
    *************************** 2. row ***************************
               PLUGIN_NAME: ndbinfo
            PLUGIN_VERSION: 0.1
             PLUGIN_STATUS: ACTIVE
               PLUGIN_TYPE: STORAGE ENGINE
       PLUGIN_TYPE_VERSION: 80024.0
            PLUGIN_LIBRARY: NULL
    PLUGIN_LIBRARY_VERSION: NULL
             PLUGIN_AUTHOR: Oracle Corporation
        PLUGIN_DESCRIPTION: MySQL Cluster system information storage engine
            PLUGIN_LICENSE: GPL
               LOAD_OPTION: ON
    *************************** 3. row ***************************
               PLUGIN_NAME: ndb_transid_mysql_connection_map
            PLUGIN_VERSION: 0.1
             PLUGIN_STATUS: ACTIVE
               PLUGIN_TYPE: INFORMATION SCHEMA
       PLUGIN_TYPE_VERSION: 80024.0
            PLUGIN_LIBRARY: NULL
    PLUGIN_LIBRARY_VERSION: NULL
             PLUGIN_AUTHOR: Oracle Corporation
        PLUGIN_DESCRIPTION: Map between MySQL connection ID and NDB transaction ID
            PLUGIN_LICENSE: GPL
               LOAD_OPTION: ON
    

    You can also use the SHOW PLUGINS statement to display this information, but the output from that statement cannot easily be filtered. See also The MySQL Plugin API, which describes where and how the information in the PLUGINS table is obtained.

You can also query the tables in the ndbinfo information database for real-time data about many NDB Cluster operations. See Section 23.5.14, “ndbinfo: The NDB Cluster Information Database”.

23.5.17 NDB Cluster Security Issues

This section discusses security considerations to take into account when setting up and running NDB Cluster.

Topics covered in this section include the following:

  • NDB Cluster and network security issues

  • Configuration issues relating to running NDB Cluster securely

  • NDB Cluster and the MySQL privilege system

  • MySQL standard security procedures as applicable to NDB Cluster

23.5.17.1 NDB Cluster Security and Networking Issues

In this section, we discuss basic network security issues as they relate to NDB Cluster. It is extremely important to remember that NDB Cluster out of the box is not secure; you or your network administrator must take the proper steps to ensure that your cluster cannot be compromised over the network.

Cluster communication protocols are inherently insecure, and no encryption or similar security measures are used in communications between nodes in the cluster. Because network speed and latency have a direct impact on the cluster's efficiency, it is also not advisable to employ SSL or other encryption to network connections between nodes, as such schemes cause slow communications.

It is also true that no authentication is used for controlling API node access to an NDB Cluster. As with encryption, the overhead of imposing authentication requirements would have an adverse impact on Cluster performance.

In addition, there is no checking of the source IP address for either of the following when accessing the cluster:

  • SQL or API nodes using free slots created by empty [mysqld] or [api] sections in the config.ini file

    This means that, if there are any empty [mysqld] or [api] sections in the config.ini file, then any API nodes (including SQL nodes) that know the management server's host name (or IP address) and port can connect to the cluster and access its data without restriction. (See Section 23.5.17.2, “NDB Cluster and MySQL Privileges”, for more information about this and related issues.)

    Note

    You can exercise some control over SQL and API node access to the cluster by specifying a HostName parameter for all [mysqld] and [api] sections in the config.ini file. However, this also means that, should you wish to connect an API node to the cluster from a previously unused host, you need to add an [api] section containing its host name to the config.ini file.

    More information is available elsewhere in this chapter about the HostName parameter. Also see Section 23.3.1, “Quick Test Setup of NDB Cluster”, for configuration examples using HostName with API nodes.

  • Any ndb_mgm client

    This means that any cluster management client that is given the management server's host name (or IP address) and port (if not the standard port) can connect to the cluster and execute any management client command. This includes commands such as ALL STOP and SHUTDOWN.

For these reasons, it is necessary to protect the cluster on the network level. The safest network configuration for Cluster is one which isolates connections between Cluster nodes from any other network communications. This can be accomplished by any of the following methods:

  1. Keeping Cluster nodes on a network that is physically separate from any public networks. This option is the most dependable; however, it is the most expensive to implement.

    We show an example of an NDB Cluster setup using such a physically segregated network here:

    Figure 23.28 NDB Cluster with Hardware Firewall

    Content is described in the surrounding text.

    This setup has two networks, one private (solid box) for the Cluster management servers and data nodes, and one public (dotted box) where the SQL nodes reside. (We show the management and data nodes connected using a gigabit switch since this provides the best performance.) Both networks are protected from the outside by a hardware firewall, sometimes also known as a network-based firewall.

    This network setup is safest because no packets can reach the cluster's management or data nodes from outside the network—and none of the cluster's internal communications can reach the outside—without going through the SQL nodes, as long as the SQL nodes do not permit any packets to be forwarded. This means, of course, that all SQL nodes must be secured against hacking attempts.

    Important

    With regard to potential security vulnerabilities, an SQL node is no different from any other MySQL server. See Section 6.1.3, “Making MySQL Secure Against Attackers”, for a description of techniques you can use to secure MySQL servers.

  2. Using one or more software firewalls (also known as host-based firewalls) to control which packets pass through to the cluster from portions of the network that do not require access to it. In this type of setup, a software firewall must be installed on every host in the cluster which might otherwise be accessible from outside the local network.

    The host-based option is the least expensive to implement, but relies purely on software to provide protection and so is the most difficult to keep secure.

    This type of network setup for NDB Cluster is illustrated here:

    Figure 23.29 NDB Cluster with Software Firewalls

    Content is described in the surrounding text.

    Using this type of network setup means that there are two zones of NDB Cluster hosts. Each cluster host must be able to communicate with all of the other machines in the cluster, but only those hosting SQL nodes (dotted box) can be permitted to have any contact with the outside, while those in the zone containing the data nodes and management nodes (solid box) must be isolated from any machines that are not part of the cluster. Applications using the cluster and user of those applications must not be permitted to have direct access to the management and data node hosts.

    To accomplish this, you must set up software firewalls that limit the traffic to the type or types shown in the following table, according to the type of node that is running on each cluster host computer:

    Table 23.67 Node types in a host-based firewall cluster configuration

    Node Type Permitted Traffic
    SQL or API node
    • It originates from the IP address of a management or data node (using any TCP or UDP port).

    • It originates from within the network in which the cluster resides and is on the port that your application is using.

    Data node or Management node
    • It originates from the IP address of a management or data node (using any TCP or UDP port).

    • It originates from the IP address of an SQL or API node.


    Any traffic other than that shown in the table for a given node type should be denied.

    The specifics of configuring a firewall vary from firewall application to firewall application, and are beyond the scope of this Manual. iptables is a very common and reliable firewall application, which is often used with APF as a front end to make configuration easier. You can (and should) consult the documentation for the software firewall that you employ, should you choose to implement an NDB Cluster network setup of this type, or of a mixed type as discussed under the next item.

  3. It is also possible to employ a combination of the first two methods, using both hardware and software to secure the cluster—that is, using both network-based and host-based firewalls. This is between the first two schemes in terms of both security level and cost. This type of network setup keeps the cluster behind the hardware firewall, but permits incoming packets to travel beyond the router connecting all cluster hosts to reach the SQL nodes.

    One possible network deployment of an NDB Cluster using hardware and software firewalls in combination is shown here:

    Figure 23.30 NDB Cluster with a Combination of Hardware and Software Firewalls

    Content is described in the surrounding text.

    In this case, you can set the rules in the hardware firewall to deny any external traffic except to SQL nodes and API nodes, and then permit traffic to them only on the ports required by your application.

Whatever network configuration you use, remember that your objective from the viewpoint of keeping the cluster secure remains the same—to prevent any unessential traffic from reaching the cluster while ensuring the most efficient communication between the nodes in the cluster.

Because NDB Cluster requires large numbers of ports to be open for communications between nodes, the recommended option is to use a segregated network. This represents the simplest way to prevent unwanted traffic from reaching the cluster.

Note

If you wish to administer an NDB Cluster remotely (that is, from outside the local network), the recommended way to do this is to use ssh or another secure login shell to access an SQL node host. From this host, you can then run the management client to access the management server safely, from within the cluster's own local network.

Even though it is possible to do so in theory, it is not recommended to use ndb_mgm to manage a Cluster directly from outside the local network on which the Cluster is running. Since neither authentication nor encryption takes place between the management client and the management server, this represents an extremely insecure means of managing the cluster, and is almost certain to be compromised sooner or later.

23.5.17.2 NDB Cluster and MySQL Privileges

In this section, we discuss how the MySQL privilege system works in relation to NDB Cluster and the implications of this for keeping an NDB Cluster secure.

Standard MySQL privileges apply to NDB Cluster tables. This includes all MySQL privilege types (SELECT privilege, UPDATE privilege, DELETE privilege, and so on) granted on the database, table, and column level. As with any other MySQL Server, user and privilege information is stored in the mysql system database. The SQL statements used to grant and revoke privileges on NDB tables, databases containing such tables, and columns within such tables are identical in all respects with the GRANT and REVOKE statements used in connection with database objects involving any (other) MySQL storage engine. The same thing is true with respect to the CREATE USER and DROP USER statements.

It is important to keep in mind that, by default, the MySQL grant tables use the MyISAM storage engine. Because of this, those tables are not normally duplicated or shared among MySQL servers acting as SQL nodes in an NDB Cluster. In other words, changes in users and their privileges do not automatically propagate between SQL nodes by default. If you wish, you can enable automatic distribution of MySQL users and privileges across NDB Cluster SQL nodes; see Section 23.5.12, “Distributed MySQL Privileges with NDB_STORED_USER”, for details.

Conversely, because there is no way in MySQL to deny privileges (privileges can either be revoked or not granted in the first place, but not denied as such), there is no special protection for NDB tables on one SQL node from users that have privileges on another SQL node; (This is true even if you are not using automatic distribution of user privileges. The definitive example of this is the MySQL root account, which can perform any action on any database object. In combination with empty [mysqld] or [api] sections of the config.ini file, this account can be especially dangerous. To understand why, consider the following scenario:

  • The config.ini file contains at least one empty [mysqld] or [api] section. This means that the NDB Cluster management server performs no checking of the host from which a MySQL Server (or other API node) accesses the NDB Cluster.

  • There is no firewall, or the firewall fails to protect against access to the NDB Cluster from hosts external to the network.

  • The host name or IP address of the NDB Cluster management server is known or can be determined from outside the network.

If these conditions are true, then anyone, anywhere can start a MySQL Server with --ndbcluster --ndb-connectstring=management_host and access this NDB Cluster. Using the MySQL root account, this person can then perform the following actions:

  • Execute metadata statements such as SHOW DATABASES statement (to obtain a list of all NDB databases on the server) or SHOW TABLES FROM some_ndb_database statement to obtain a list of all NDB tables in a given database

  • Run any legal MySQL statements on any of the discovered tables, such as:

    • SELECT * FROM some_table to read all the data from any table

    • DELETE FROM some_table to delete all the data from a table

    • DESCRIBE some_table or SHOW CREATE TABLE some_table to determine the table schema

    • UPDATE some_table SET column1 = some_value to fill a table column with garbage data; this could actually cause much greater damage than simply deleting all the data

      More insidious variations might include statements like these:

      UPDATE some_table SET an_int_column = an_int_column + 1
      

      or

      UPDATE some_table SET a_varchar_column = REVERSE(a_varchar_column)
      

      Such malicious statements are limited only by the imagination of the attacker.

    The only tables that would be safe from this sort of mayhem would be those tables that were created using storage engines other than NDB, and so not visible to a rogue SQL node.

    A user who can log in as root can also access the INFORMATION_SCHEMA database and its tables, and so obtain information about databases, tables, stored routines, scheduled events, and any other database objects for which metadata is stored in INFORMATION_SCHEMA.

    It is also a very good idea to use different passwords for the root accounts on different NDB Cluster SQL nodes unless you are using distributed privileges.

In sum, you cannot have a safe NDB Cluster if it is directly accessible from outside your local network.

Important

Never leave the MySQL root account password empty. This is just as true when running MySQL as an NDB Cluster SQL node as it is when running it as a standalone (non-Cluster) MySQL Server, and should be done as part of the MySQL installation process before configuring the MySQL Server as an SQL node in an NDB Cluster.

If you wish to employ NDB Cluster's distributed privilege capabilities, you should not simply convert the system tables in the mysql database to use the NDB storage engine manually. Use the stored procedure provided for this purpose instead; see Section 23.5.12, “Distributed MySQL Privileges with NDB_STORED_USER”.

Otherwise, if you need to synchronize mysql system tables between SQL nodes, you can use standard MySQL replication to do so, or employ a script to copy table entries between the MySQL servers.

Summary.  The most important points to remember regarding the MySQL privilege system with regard to NDB Cluster are listed here:

  1. Users and privileges established on one SQL node do not automatically exist or take effect on other SQL nodes in the cluster. Conversely, removing a user or privilege on one SQL node in the cluster does not remove the user or privilege from any other SQL nodes.

  2. You can distribute MySQL users and privileges among SQL nodes using the SQL script, and the stored procedures it contains, that are supplied for this purpose in the NDB Cluster distribution.

  3. Once a MySQL user is granted privileges on an NDB table from one SQL node in an NDB Cluster, that user can see any data in that table regardless of the SQL node from which the data originated, even if you are not using privilege distribution.

23.5.17.3 NDB Cluster and MySQL Security Procedures

In this section, we discuss MySQL standard security procedures as they apply to running NDB Cluster.

In general, any standard procedure for running MySQL securely also applies to running a MySQL Server as part of an NDB Cluster. First and foremost, you should always run a MySQL Server as the mysql operating system user; this is no different from running MySQL in a standard (non-Cluster) environment. The mysql system account should be uniquely and clearly defined. Fortunately, this is the default behavior for a new MySQL installation. You can verify that the mysqld process is running as the mysql operating system user by using the system command such as the one shown here:

shell> ps aux | grep mysql
root     10467  0.0  0.1   3616  1380 pts/3    S    11:53   0:00 \
  /bin/sh ./mysqld_safe --ndbcluster --ndb-connectstring=localhost:1186
mysql    10512  0.2  2.5  58528 26636 pts/3    Sl   11:53   0:00 \
  /usr/local/mysql/libexec/mysqld --basedir=/usr/local/mysql \
  --datadir=/usr/local/mysql/var --user=mysql --ndbcluster \
  --ndb-connectstring=localhost:1186 --pid-file=/usr/local/mysql/var/mothra.pid \
  --log-error=/usr/local/mysql/var/mothra.err
jon      10579  0.0  0.0   2736   688 pts/0    S+   11:54   0:00 grep mysql

If the mysqld process is running as any other user than mysql, you should immediately shut it down and restart it as the mysql user. If this user does not exist on the system, the mysql user account should be created, and this user should be part of the mysql user group; in this case, you should also make sure that the MySQL data directory on this system (as set using the --datadir option for mysqld) is owned by the mysql user, and that the SQL node's my.cnf file includes user=mysql in the [mysqld] section. Alternatively, you can start the MySQL server process with --user=mysql on the command line, but it is preferable to use the my.cnf option, since you might forget to use the command-line option and so have mysqld running as another user unintentionally. The mysqld_safe startup script forces MySQL to run as the mysql user.

Important

Never run mysqld as the system root user. Doing so means that potentially any file on the system can be read by MySQL, and thus—should MySQL be compromised—by an attacker.

As mentioned in the previous section (see Section 23.5.17.2, “NDB Cluster and MySQL Privileges”), you should always set a root password for the MySQL Server as soon as you have it running. You should also delete the anonymous user account that is installed by default. You can accomplish these tasks using the following statements:

shell> mysql -u root

mysql> UPDATE mysql.user
    ->     SET Password=PASSWORD('secure_password')
    ->     WHERE User='root';

mysql> DELETE FROM mysql.user
    ->     WHERE User='';

mysql> FLUSH PRIVILEGES;

Be very careful when executing the DELETE statement not to omit the WHERE clause, or you risk deleting all MySQL users. Be sure to run the FLUSH PRIVILEGES statement as soon as you have modified the mysql.user table, so that the changes take immediate effect. Without FLUSH PRIVILEGES, the changes do not take effect until the next time that the server is restarted.

Note

Many of the NDB Cluster utilities such as ndb_show_tables, ndb_desc, and ndb_select_all also work without authentication and can reveal table names, schemas, and data. By default these are installed on Unix-style systems with the permissions wxr-xr-x (755), which means they can be executed by any user that can access the mysql/bin directory.

See Section 23.4, “NDB Cluster Programs”, for more information about these utilities.

23.6 NDB Cluster Replication

NDB Cluster supports asynchronous replication, more usually referred to simply as replication. This section explains how to set up and manage a configuration in which one group of computers operating as an NDB Cluster replicates to a second computer or group of computers. We assume some familiarity on the part of the reader with standard MySQL replication as discussed elsewhere in this Manual. (See Chapter 17, Replication).

Note

NDB Cluster does not support replication using GTIDs; semisynchronous replication and group replication are also not supported by the NDB storage engine.

Normal (non-clustered) replication involves a source server and a replica server, the source being so named because operations and data to be replicated originate with it, and the replica being the recipient of these. In NDB Cluster, replication is conceptually very similar but can be more complex in practice, as it may be extended to cover a number of different configurations including replicating between two complete clusters. Although an NDB Cluster itself depends on the NDB storage engine for clustering functionality, it is not necessary to use NDB as the storage engine for the replica's copies of the replicated tables (see Replication from NDB to other storage engines). However, for maximum availability, it is possible (and preferable) to replicate from one NDB Cluster to another, and it is this scenario that we discuss, as shown in the following figure:

Figure 23.31 NDB Cluster-to-Cluster Replication Layout

Much of the content is described in the surrounding text. It visualizes how a MySQL source is replicated. The replica differs in that it shows an I/O thread pointing to a relay binary log which points to an SQL thread. In addition, while the binary log points to and from the NDBCLUSTER engine on the source server, on the replica it points directly to an SQL node (MySQL server).

In this scenario, the replication process is one in which successive states of a source cluster are logged and saved to a replica cluster. This process is accomplished by a special thread known as the NDB binary log injector thread, which runs on each MySQL server and produces a binary log (binlog). This thread ensures that all changes in the cluster producing the binary log—and not just those changes that are effected through the MySQL Server—are inserted into the binary log with the correct serialization order. We refer to the MySQL source and replica servers as replication servers or replication nodes, and the data flow or line of communication between them as a replication channel.

For information about performing point-in-time recovery with NDB Cluster and NDB Cluster Replication, see Section 23.6.9.2, “Point-In-Time Recovery Using NDB Cluster Replication”.

NDB API replica status variables.  NDB API counters can provide enhanced monitoring capabilities on replica clusters. These counters are implemented as NDB statistics _slave status variables, as seen in the output of SHOW STATUS, or in the results of queries against the Performance Schema session_status or global_status table in a mysql client session connected to a MySQL Server that is acting as a replica in NDB Cluster Replication. By comparing the values of these status variables before and after the execution of statements affecting replicated NDB tables, you can observe the corresponding actions taken on the NDB API level by the replica, which can be useful when monitoring or troubleshooting NDB Cluster Replication. Section 23.5.13, “NDB API Statistics Counters and Variables”, provides additional information.

Replication from NDB to non-NDB tables.  It is possible to replicate NDB tables from an NDB Cluster acting as the replication source to tables using other MySQL storage engines such as InnoDB or MyISAM on a replica mysqld. This is subject to a number of conditions; see Replication from NDB to other storage engines, and Replication from NDB to a nontransactional storage engine, for more information.

23.6.1 NDB Cluster Replication: Abbreviations and Symbols

Throughout this section, we use the following abbreviations or symbols for referring to the source and replica clusters, and to processes and commands run on the clusters or cluster nodes:

Table 23.68 Abbreviations used throughout this section referring to source and replica clusters, and to processes and commands run on cluster nodes

Symbol or Abbreviation Description (Refers to...)
S The cluster serving as the (primary) replication source
R The cluster acting as the (primary) replica
shellS> Shell command to be issued on the source cluster
mysqlS> MySQL client command issued on a single MySQL server running as an SQL node on the source cluster
mysqlS*> MySQL client command to be issued on all SQL nodes participating in the replication source cluster
shellR> Shell command to be issued on the replica cluster
mysqlR> MySQL client command issued on a single MySQL server running as an SQL node on the replica cluster
mysqlR*> MySQL client command to be issued on all SQL nodes participating in the replica cluster
C Primary replication channel
C' Secondary replication channel
S' Secondary replication source
R' Secondary replica

23.6.2 General Requirements for NDB Cluster Replication

A replication channel requires two MySQL servers acting as replication servers (one each for the source and replica). For example, this means that in the case of a replication setup with two replication channels (to provide an extra channel for redundancy), there are a total of four replication nodes, two per cluster.

Replication of an NDB Cluster as described in this section and those following is dependent on row-based replication. This means that the replication source MySQL server must be running with --binlog-format=ROW or --binlog-format=MIXED, as described in Section 23.6.6, “Starting NDB Cluster Replication (Single Replication Channel)”. For general information about row-based replication, see Section 17.2.1, “Replication Formats”.

Important

If you attempt to use NDB Cluster Replication with --binlog-format=STATEMENT, replication fails to work properly because the ndb_binlog_index table on the source cluster and the epoch column of the ndb_apply_status table on the replica cluster are not updated (see Section 23.6.4, “NDB Cluster Replication Schema and Tables”). Instead, only updates on the MySQL server acting as the replication source propagate to the replica, and no updates from any other SQL nodes in the source cluster are replicated.

The default value for the --binlog-format option is MIXED.

Each MySQL server used for replication in either cluster must be uniquely identified among all the MySQL replication servers participating in either cluster (you cannot have replication servers on both the source and replica clusters sharing the same ID). This can be done by starting each SQL node using the --server-id=id option, where id is a unique integer. Although it is not strictly necessary, we assume for purposes of this discussion that all NDB Cluster binaries are of the same release version.

It is generally true in MySQL Replication that both MySQL servers (mysqld processes) involved must be compatible with one another with respect to both the version of the replication protocol used and the SQL feature sets which they support (see Section 17.5.2, “Replication Compatibility Between MySQL Versions”). It is due to such differences between the binaries in the NDB Cluster and MySQL Server 8.0 distributions that NDB Cluster Replication has the additional requirement that both mysqld binaries come from an NDB Cluster distribution. The simplest and easiest way to assure that the mysqld servers are compatible is to use the same NDB Cluster distribution for all source and replica mysqld binaries.

We assume that the replica server or cluster is dedicated to replication of the source cluster, and that no other data is being stored on it.

All NDB tables being replicated must be created using a MySQL server and client. Tables and other database objects created using the NDB API (with, for example, Dictionary::createTable()) are not visible to a MySQL server and so are not replicated. Updates by NDB API applications to existing tables that were created using a MySQL server can be replicated.

Note

It is possible to replicate an NDB Cluster using statement-based replication. However, in this case, the following restrictions apply:

  • All updates to data rows on the cluster acting as the source must be directed to a single MySQL server.

  • It is not possible to replicate a cluster using multiple simultaneous MySQL replication processes.

  • Only changes made at the SQL level are replicated.

These are in addition to the other limitations of statement-based replication as opposed to row-based replication; see Section 17.2.1.1, “Advantages and Disadvantages of Statement-Based and Row-Based Replication”, for more specific information concerning the differences between the two replication formats.

23.6.3 Known Issues in NDB Cluster Replication

This section discusses known problems or issues when using replication with NDB Cluster.

Loss of connection between source and replica.  A loss of connection can occur either between the source cluster SQL node and the replica cluster SQL node, or between the source SQL node and the data nodes of the source cluster. In the latter case, this can occur not only as a result of loss of physical connection (for example, a broken network cable), but due to the overflow of data node event buffers; if the SQL node is too slow to respond, it may be dropped by the cluster (this is controllable to some degree by adjusting the MaxBufferedEpochs and TimeBetweenEpochs configuration parameters). If this occurs, it is entirely possible for new data to be inserted into the source cluster without being recorded in the source SQL node's binary log. For this reason, to guarantee high availability, it is extremely important to maintain a backup replication channel, to monitor the primary channel, and to fail over to the secondary replication channel when necessary to keep the replica cluster synchronized with the source. NDB Cluster is not designed to perform such monitoring on its own; for this, an external application is required.

The source SQL node issues a gap event when connecting or reconnecting to the source cluster. (A gap event is a type of incident event, which indicates an incident that occurs that affects the contents of the database but that cannot easily be represented as a set of changes. Examples of incidents are server failures, database resynchronization, some software updates, and some hardware changes.) When the replica encounters a gap in the replication log, it stops with an error message. This message is available in the output of SHOW REPLICA | SLAVE STATUS, and indicates that the SQL thread has stopped due to an incident registered in the replication stream, and that manual intervention is required. See Section 23.6.8, “Implementing Failover with NDB Cluster Replication”, for more information about what to do in such circumstances.

Important

Because NDB Cluster is not designed on its own to monitor replication status or provide failover, if high availability is a requirement for the replica server or cluster, then you must set up multiple replication lines, monitor the source mysqld on the primary replication line, and be prepared fail over to a secondary line if and as necessary. This must be done manually, or possibly by means of a third-party application. For information about implementing this type of setup, see Section 23.6.7, “Using Two Replication Channels for NDB Cluster Replication”, and Section 23.6.8, “Implementing Failover with NDB Cluster Replication”.

If you are replicating from a standalone MySQL server to an NDB Cluster, one channel is usually sufficient.

Circular replication.  NDB Cluster Replication supports circular replication, as shown in the next example. The replication setup involves three NDB Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication source for Cluster 2, Cluster 2 acts as the source for Cluster 3, and Cluster 3 acts as the source for Cluster 1, thus completing the circle. Each NDB Cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3.

Circular replication using these clusters is supported as long as the following conditions are met:

  • The SQL nodes on all source and replica clusters are the same.

  • All SQL nodes acting as sources and replicas are started with the log_slave_updates system variable enabled.

This type of circular replication setup is shown in the following diagram:

Figure 23.32 NDB Cluster Circular Replication With All Sources As Replicas

Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that all sources are also replicas.

In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the curved arrows in the diagram) directly connects all SQL nodes used as sources and replicas.

It should also be possible to set up circular replication in which not all source SQL nodes are also replicas, as shown here:

Figure 23.33 NDB Cluster Circular Replication Where Not All Sources Are Replicas

Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that not all sources are replicas.

In this case, different SQL nodes in each cluster are used as sources and replicas. However, you must not start any of the SQL nodes with the log_slave_updates system variable enabled. This type of circular replication scheme for NDB Cluster, in which the line of replication (again indicated by the curved arrows in the diagram) is discontinuous, should be possible, but it should be noted that it has not yet been thoroughly tested and must therefore still be considered experimental.

Note

The NDB storage engine uses idempotent execution mode, which suppresses duplicate-key and other errors that otherwise break circular replication of NDB Cluster. This is equivalent to setting the global slave_exec_mode system variable to IDEMPOTENT, although this is not necessary in NDB Cluster replication, since NDB Cluster sets this variable automatically and ignores any attempts to set it explicitly.

NDB Cluster replication and primary keys.  In the event of a node failure, errors in replication of NDB tables without primary keys can still occur, due to the possibility of duplicate rows being inserted in such cases. For this reason, it is highly recommended that all NDB tables being replicated have explicit primary keys.

NDB Cluster Replication and Unique Keys.  In older versions of NDB Cluster, operations that updated values of unique key columns of NDB tables could result in duplicate-key errors when replicated. This issue is solved for replication between NDB tables by deferring unique key checks until after all table row updates have been performed.

Deferring constraints in this way is currently supported only by NDB. Thus, updates of unique keys when replicating from NDB to a different storage engine such as InnoDB or MyISAM are still not supported.

The problem encountered when replicating without deferred checking of unique key updates can be illustrated using NDB table such as t, is created and populated on the source (and transmitted to a replica that does not support deferred unique key updates) as shown here:

CREATE TABLE t (
    p INT PRIMARY KEY,
    c INT,
    UNIQUE KEY u (c)
)   ENGINE NDB;

INSERT INTO t
    VALUES (1,1), (2,2), (3,3), (4,4), (5,5);

The following UPDATE statement on t succeeds on the source, since the rows affected are processed in the order determined by the ORDER BY option, performed over the entire table:

UPDATE t SET c = c - 1 ORDER BY p;

The same statement fails with a duplicate key error or other constraint violation on the replica, because the ordering of the row updates is performed for one partition at a time, rather than for the table as a whole.

Note

Every NDB table is implicitly partitioned by key when it is created. See Section 24.2.5, “KEY Partitioning”, for more information.

GTIDs not supported.  Replication using global transaction IDs is not compatible with the NDB storage engine, and is not supported. Enabling GTIDs is likely to cause NDB Cluster Replication to fail.

Multithreaded replicas not supported.  NDB Cluster does not support multithreaded replicas, and setting related system variables such as slave_parallel_workers, slave_checkpoint_group, and slave_checkpoint_group (or the equivalent mysqld startup options) has no effect.

This is because the replica may not be able to separate transactions occurring in one database from those in another if they are written within the same epoch. In addition, every transaction handled by the NDB storage engine involves at least two databases—the target database and the mysql system database—due to the requirement for updating the mysql.ndb_apply_status table (see Section 23.6.4, “NDB Cluster Replication Schema and Tables”). This in turn breaks the requirement for multithreading that the transaction is specific to a given database.

Restarting with --initial.  Restarting the cluster with the --initial option causes the sequence of GCI and epoch numbers to start over from 0. (This is generally true of NDB Cluster and not limited to replication scenarios involving Cluster.) The MySQL servers involved in replication should in this case be restarted. After this, you should use the RESET MASTER and RESET REPLICA | SLAVE statements to clear the invalid ndb_binlog_index and ndb_apply_status tables, respectively.

Replication from NDB to other storage engines.  It is possible to replicate an NDB table on the source to a table using a different storage engine on the replica, taking into account the restrictions listed here:

  • Multi-source and circular replication are not supported (tables on both the source and the replica must use the NDB storage engine for this to work).

  • Using a storage engine which does not perform binary logging for tables on the replica requires special handling.

  • Use of a nontransactional storage engine for tables on the replica also requires special handling.

  • The source mysqld must be started with --ndb-log-update-as-write=0 or --ndb-log-update-as-write=OFF.

The next few paragraphs provide additional information about each of the issues just described.

Multiple sources not supported when replicating NDB to other storage engines.  For replication from NDB to a different storage engine, the relationship between the two databases must be one-to-one. This means that bidirectional or circular replication is not supported between NDB Cluster and other storage engines.

In addition, it is not possible to configure more than one replication channel when replicating between NDB and a different storage engine. (An NDB Cluster database can simultaneously replicate to multiple NDB Cluster databases.) If the source uses NDB tables, it is still possible to have more than one MySQL Server maintain a binary log of all changes, but for the replica to change sources (fail over), the new source-replica relationship must be explicitly defined on the replica.

Replicating NDB tables to a storage engine that does not perform binary logging.  If you attempt to replicate from an NDB Cluster to a replica that uses a storage engine that does not handle its own binary logging, the replication process aborts with the error Binary logging not possible ... Statement cannot be written atomically since more than one engine involved and at least one engine is self-logging (Error 1595). It is possible to work around this issue in one of the following ways:

  • Turn off binary logging on the replica.  This can be accomplished by setting sql_log_bin = 0.

  • Change the storage engine used for the mysql.ndb_apply_status table.  Causing this table to use an engine that does not handle its own binary logging can also eliminate the conflict. This can be done by issuing a statement such as ALTER TABLE mysql.ndb_apply_status ENGINE=MyISAM on the replica. It is safe to do this when using a storage engine other than NDB on the replica, since you do not need to worry about keeping multiple replicas synchronized.

  • Filter out changes to the mysql.ndb_apply_status table on the replica.  This can be done by starting the replica with --replicate-ignore-table=mysql.ndb_apply_status. If you need for other tables to be ignored by replication, you might wish to use an appropriate --replicate-wild-ignore-table option instead.

Important

You should not disable replication or binary logging of mysql.ndb_apply_status or change the storage engine used for this table when replicating from one NDB Cluster to another. See Replication and binary log filtering rules with replication between NDB Clusters, for details.

Replication from NDB to a nontransactional storage engine.  When replicating from NDB to a nontransactional storage engine such as MyISAM, you may encounter unnecessary duplicate key errors when replicating INSERT ... ON DUPLICATE KEY UPDATE statements. You can suppress these by using --ndb-log-update-as-write=0, which forces updates to be logged as writes, rather than as updates.

Replication and binary log filtering rules with replication between NDB Clusters.  If you are using any of the options --replicate-do-*, --replicate-ignore-*, --binlog-do-db, or --binlog-ignore-db to filter databases or tables being replicated, you must take care not to block replication or binary logging of the mysql.ndb_apply_status, which is required for replication between NDB Clusters to operate properly. In particular, you must keep in mind the following:

  1. Using --replicate-do-db=db_name (and no other --replicate-do-* or --replicate-ignore-* options) means that only tables in database db_name are replicated. In this case, you should also use --replicate-do-db=mysql, --binlog-do-db=mysql, or --replicate-do-table=mysql.ndb_apply_status to ensure that mysql.ndb_apply_status is populated on replicas.

    Using --binlog-do-db=db_name (and no other --binlog-do-db options) means that changes only to tables in database db_name are written to the binary log. In this case, you should also use --replicate-do-db=mysql, --binlog-do-db=mysql, or --replicate-do-table=mysql.ndb_apply_status to ensure that mysql.ndb_apply_status is populated on replicas.

  2. Using --replicate-ignore-db=mysql means that no tables in the mysql database are replicated. In this case, you should also use --replicate-do-table=mysql.ndb_apply_status to ensure that mysql.ndb_apply_status is replicated.

    Using --binlog-ignore-db=mysql means that no changes to tables in the mysql database are written to the binary log. In this case, you should also use --replicate-do-table=mysql.ndb_apply_status to ensure that mysql.ndb_apply_status is replicated.

You should also remember that each replication rule requires the following:

  1. Its own --replicate-do-* or --replicate-ignore-* option, and that multiple rules cannot be expressed in a single replication filtering option. For information about these rules, see Section 17.1.6, “Replication and Binary Logging Options and Variables”.

  2. Its own --binlog-do-db or --binlog-ignore-db option, and that multiple rules cannot be expressed in a single binary log filtering option. For information about these rules, see Section 5.4.4, “The Binary Log”.

If you are replicating an NDB Cluster to a replica that uses a storage engine other than NDB, the considerations just given previously may not apply, as discussed elsewhere in this section.

NDB Cluster Replication and IPv6.  Beginning with NDB 8.0.22, all types of NDB Cluster nodes support IPv6; this includes management nodes, data nodes, and API or SQL nodes.

Prior to NDB 8.0.22, the NDB API and MGM API (and thus data nodes and management nodes) do not support IPv6, although MySQL Servers—including those acting as SQL nodes in an NDB Cluster —can use IPv6 to contact other MySQL Servers. In versions of NDB Cluster prior to 8.0.22, you can replicate between clusters using IPv6 to connect the SQL nodes acting as source and replica as shown by the dotted arrow in the following diagram:

Figure 23.34 Replication Between SQL Nodes Connected Using IPv6

Most content is described in the surrounding text. The dotted line representing a MySQL-to-MySQL IPv6 connection is between two nodes, one each from the source and replica clusters. All connections within the cluster, such as data node to data node or data node to management node, are connected with solid lines to indicate IPv4 connections only.

Prior to NDB 8.0.22, all connections originating within the NDB Cluster —represented in the preceding diagram by solid arrows—must use IPv4. In other words, all NDB Cluster data nodes, management servers, and management clients must be accessible from one another using IPv4. In addition, SQL nodes must use IPv4 to communicate with the cluster. In NDB 8.0.22 and later, these restrictions no longer apply; in addition, any applications written using the NDB and MGM APIs can be written and deployed assuming an IPv6-only environment.

Attribute promotion and demotion.  NDB Cluster Replication includes support for attribute promotion and demotion. The implementation of the latter distinguishes between lossy and non-lossy type conversions, and their use on the replica can be controlled by setting the slave_type_conversions global server system variable.

For more information about attribute promotion and demotion in NDB Cluster, see Row-based replication: attribute promotion and demotion.

NDB, unlike InnoDB or MyISAM, does not write changes to virtual columns to the binary log; however, this has no detrimental effects on NDB Cluster Replication or replication between NDB and other storage engines. Changes to stored generated columns are logged.

23.6.4 NDB Cluster Replication Schema and Tables

Replication in NDB Cluster makes use of a number of dedicated tables in the mysql database on each MySQL Server instance acting as an SQL node in both the cluster being replicated and in the replica. This is true regardless of whether the replica is a single server or a cluster. These tables are created during the MySQL installation process, and include a table for storing the binary log's indexing data. Since the ndb_binlog_index table is local to each MySQL server and does not participate in clustering, it uses the InnoDB storage engine. This means that it must be created separately on each mysqld participating in the source cluster. (The binary log itself contains updates from all MySQL servers in the cluster to be replicated.) This table is defined as follows:

CREATE TABLE `ndb_binlog_index` (
    `Position` BIGINT(20) UNSIGNED NOT NULL,
    `File` VARCHAR(255) NOT NULL,
    `epoch` BIGINT(20) UNSIGNED NOT NULL,
    `inserts` INT(10) UNSIGNED NOT NULL,
    `updates` INT(10) UNSIGNED NOT NULL,
    `deletes` INT(10) UNSIGNED NOT NULL,
    `schemaops` INT(10) UNSIGNED NOT NULL,
    `orig_server_id` INT(10) UNSIGNED NOT NULL,
    `orig_epoch` BIGINT(20) UNSIGNED NOT NULL,
    `gci` INT(10) UNSIGNED NOT NULL,
    `next_position` bigint(20) unsigned NOT NULL,
    `next_file` varchar(255) NOT NULL,
    PRIMARY KEY (`epoch`,`orig_server_id`,`orig_epoch`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Note

If you are upgrading from an older release (prior to NDB 7.5.2), perform the MySQL upgrade procedure and ensure that the system tables are upgraded. (As of MySQL 8.0.16, start the server with the --upgrade=FORCE option. Prior to MySQL 8.0.16, invoke mysql_upgrade with the --force and --upgrade-system-tables options after starting the server.) The system table upgrade causes an ALTER TABLE ... ENGINE=INNODB statement to be executed for this table. Use of the MyISAM storage engine for this table continues to be supported for backward compatibility.

ndb_binlog_index may require additional disk space after being converted to InnoDB. If this becomes an issue, you may be able to conserve space by using an InnoDB tablespace for this table, changing its ROW_FORMAT to COMPRESSED, or both. For more information, see Section 13.1.21, “CREATE TABLESPACE Statement”, and Section 13.1.20, “CREATE TABLE Statement”, as well as Section 15.6.3, “Tablespaces”.

The size of the ndb_binlog_index table is dependent on the number of epochs per binary log file and the number of binary log files. The number of epochs per binary log file normally depends on the amount of binary log generated per epoch and the size of the binary log file, with smaller epochs resulting in more epochs per file. You should be aware that empty epochs produce inserts to the ndb_binlog_index table, even when the --ndb-log-empty-epochs option is OFF, meaning that the number of entries per file depends on the length of time that the file is in use; this relationship can be represented by the formula shown here:

[number of epochs per file] = [time spent per file] / TimeBetweenEpochs

A busy NDB Cluster writes to the binary log regularly and presumably rotates binary log files more quickly than a quiet one. This means that a quiet NDB Cluster with --ndb-log-empty-epochs=ON can actually have a much higher number of ndb_binlog_index rows per file than one with a great deal of activity.

When mysqld is started with the --ndb-log-orig option, the orig_server_id and orig_epoch columns store, respectively, the ID of the server on which the event originated and the epoch in which the event took place on the originating server, which is useful in NDB Cluster replication setups employing multiple sources. The SELECT statement used to find the closest binary log position to the highest applied epoch on the replica in a multi-source setup (see Section 23.6.10, “NDB Cluster Replication: Bidrectional and Circular Replication”) employs these two columns, which are not indexed. This can lead to performance issues when trying to fail over, since the query must perform a table scan, especially when the source has been running with --ndb-log-empty-epochs=ON. You can improve multi-source failover times by adding an index to these columns, as shown here:

ALTER TABLE mysql.ndb_binlog_index
    ADD INDEX orig_lookup USING BTREE (orig_server_id, orig_epoch);

Adding this index provides no benefit when replicating from a single source to a single replica, since the query used to get the binary log position in such cases makes no use of orig_server_id or orig_epoch.

See Section 23.6.8, “Implementing Failover with NDB Cluster Replication”, for more information about using the next_position and next_file columns.

The following figure shows the relationship of the NDB Cluster replication source server, its binary log injector thread, and the mysql.ndb_binlog_index table.

Figure 23.35 The Replication Source Cluster

Most concepts are described in the surrounding text. This complex image has three main areas. The top area is divided into three sections: MySQL Server (mysqld), NDBCLUSTER table handler, and mutex. A connection thread connects these, and receiver and injector threads connect the NDBCLUSTER table handler and mutex. The bottom area shows four data nodes (ndbd). They all produce events represented by arrows pointing to the receiver thread, and the receiver thread also points to the connection and injector threads. One node sends and receives to the mutex area. The arrow representing the injector thread points to a binary log as well as the ndb_binlog_index table, which is described in the surrounding text.

An additional table, named ndb_apply_status, is used to keep a record of the operations that have been replicated from the source to the replica. Unlike the case with ndb_binlog_index, the data in this table is not specific to any one SQL node in the (replica) cluster, and so ndb_apply_status can use the NDBCLUSTER storage engine, as shown here:

CREATE TABLE `ndb_apply_status` (
    `server_id`   INT(10) UNSIGNED NOT NULL,
    `epoch`       BIGINT(20) UNSIGNED NOT NULL,
    `log_name`    VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL,
    `start_pos`   BIGINT(20) UNSIGNED NOT NULL,
    `end_pos`     BIGINT(20) UNSIGNED NOT NULL,
    PRIMARY KEY (`server_id`) USING HASH
) ENGINE=NDBCLUSTER   DEFAULT CHARSET=latin1;

The ndb_apply_status table is populated only on replicas, which means that, on the source, this table never contains any rows; thus, there is no need to allot any DataMemory to ndb_apply_status there.

Because this table is populated from data originating on the source, it should be allowed to replicate; any replication filtering or binary log filtering rules that inadvertently prevent the replica from updating ndb_apply_status, or that prevent the source from writing into the binary log may prevent replication between clusters from operating properly. For more information about potential problems arising from such filtering rules, see Replication and binary log filtering rules with replication between NDB Clusters.

The ndb_binlog_index and ndb_apply_status tables are created in the mysql database because they should not be explicitly replicated by the user. User intervention is normally not required to create or maintain either of these tables, since both are maintained by the NDB binary log (binlog) injector thread. This keeps the source mysqld process updated to changes performed by the NDB storage engine. The NDB binlog injector thread receives events directly from the NDB storage engine. The NDB injector is responsible for capturing all the data events within the cluster, and ensures that all events which change, insert, or delete data are recorded in the ndb_binlog_index table. The replica I/O thread transfers the events from the source's binary log to the replica's relay log.

Even though ndb_binlog_index and ndb_apply_status are created and maintained automatically, it is advisable to check for the existence and integrity of these tables as an initial step in preparing an NDB Cluster for replication. It is possible to view event data recorded in the binary log by querying the mysql.ndb_binlog_index table directly on the source. This can be also be accomplished using the SHOW BINLOG EVENTS statement on either the source or replica SQL node. (See Section 13.7.7.2, “SHOW BINLOG EVENTS Statement”.)

You can also obtain useful information from the output of SHOW ENGINE NDB STATUS.

Note

When performing schema changes on NDB tables, applications should wait until the ALTER TABLE statement has returned in the MySQL client connection that issued the statement before attempting to use the updated definition of the table.

If the ndb_apply_status table does not exist on the replica, ndb_restore re-creates it.

Conflict resolution for NDB Cluster Replication requires the presence of an additional mysql.ndb_replication table. Currently, this table must be created manually. For information about how to do this, see Section 23.6.11, “NDB Cluster Replication Conflict Resolution”.

23.6.5 Preparing the NDB Cluster for Replication

Preparing the NDB Cluster for replication consists of the following steps:

  1. Check all MySQL servers for version compatibility (see Section 23.6.2, “General Requirements for NDB Cluster Replication”).

  2. Create a replication account on the source Cluster with the appropriate privileges, using the following two SQL statements:

    mysqlS> CREATE USER 'replica_user'@'replica_host'
         -> IDENTIFIED BY 'replica_password';
    
    mysqlS> GRANT REPLICATION SLAVE ON *.*
         -> TO 'replica_user'@'replica_host';
    

    In the previous statement, replica_user is the replication account user name, replica_host is the host name or IP address of the replica, and replica_password is the password to assign to this account.

    For example, to create a replica user account with the name myreplica, logging in from the host named replica-host, and using the password 53cr37, use the following CREATE USER and GRANT statements:

    mysqlS> CREATE USER 'myreplica'@'replica-host'
         -> IDENTIFIED BY '53cr37';
    
    mysqlS> GRANT REPLICATION SLAVE ON *.*
         -> TO 'myreplica'@'replica-host';
    

    For security reasons, it is preferable to use a unique user account—not employed for any other purpose—for the replication account.

  3. Set up the replica to use the source. Using the mysql client, this can be accomplished with the the following CHANGE MASTER TO statement:

    mysqlR> CHANGE MASTER TO
         -> MASTER_HOST='source_host',
         -> MASTER_PORT=source_port,
         -> MASTER_USER='replica_user',
         -> MASTER_PASSWORD='replica_password';
    

    In the previous statement, source_host is the host name or IP address of the replication source, source_port is the port for the replica to use when connecting to the source, replica_user is the user name set up for the replica on the source, and replica_password is the password set for that user account in the previous step.

    For example, to tell the replica to use the MySQL server whose host name is rep-source with the replication account created in the previous step, use the following statement:

    mysqlR> CHANGE MASTER TO
         -> MASTER_HOST='rep-source',
         -> MASTER_PORT=3306,
         -> MASTER_USER='myreplica',
         -> MASTER_PASSWORD='53cr37';
    

    For a complete list of options that can be used with this statement, see Section 13.4.2.1, “CHANGE MASTER TO Statement”.

    To provide replication backup capability, you also need to add an --ndb-connectstring option to the replica's my.cnf file prior to starting the replication process. See Section 23.6.9, “NDB Cluster Backups With NDB Cluster Replication”, for details.

    For additional options that can be set in my.cnf for replicas, see Section 17.1.6, “Replication and Binary Logging Options and Variables”.

  4. If the source cluster is already in use, you can create a backup of the source and load this onto the replica to cut down on the amount of time required for the replica to synchronize itself with the source. If the replica is also running NDB Cluster, this can be accomplished using the backup and restore procedure described in Section 23.6.9, “NDB Cluster Backups With NDB Cluster Replication”.

    ndb-connectstring=management_host[:port]
    

    In the event that you are not using NDB Cluster on the replica, you can create a backup with this command on the source:

    shellS> mysqldump --master-data=1
    

    Then import the resulting data dump onto the replica by copying the dump file over to it. After this, you can use the mysql client to import the data from the dumpfile into the replica database as shown here, where dump_file is the name of the file that was generated using mysqldump on the source, and db_name is the name of the database to be replicated:

    shellR> mysql -u root -p db_name < dump_file
    

    For a complete list of options to use with mysqldump, see Section 4.5.4, “mysqldump — A Database Backup Program”.

    Note

    If you copy the data to the replica in this fashion, you should make sure that the replica is started with the --skip-slave-start option on the command line, or else include skip-slave-start in the replica's my.cnf file to keep it from trying to connect to the source to begin replicating before all the data has been loaded. Once the data loading has completed, follow the additional steps outlined in the next two sections.

  5. Ensure that each MySQL server acting as a replication source is assigned a unique server ID, and has binary logging enabled, using the row-based format. (See Section 17.2.1, “Replication Formats”.) In addition, we recommend enabling the slave_allow_batching system variable, and possibly increasing the values used with the --ndb-batch-size and --ndb-blob-write-batch-bytes options as well. All of these options can be set either in the source server's my.cnf file, or on the command line when starting the source mysqld process. See Section 23.6.6, “Starting NDB Cluster Replication (Single Replication Channel)”, for more information.

23.6.6 Starting NDB Cluster Replication (Single Replication Channel)

This section outlines the procedure for starting NDB Cluster replication using a single replication channel.

  1. Start the MySQL replication source server by issuing this command:

    shellS> mysqld --ndbcluster --server-id=id \
            --log-bin --ndb-log-bin &
    

    In the previous statement, id is this server's unique ID (see Section 23.6.2, “General Requirements for NDB Cluster Replication”). This starts the server's mysqld process with binary logging enabled using the proper logging format. It is also necessary in NDB 8.0 to enable logging of updates to NDB tables explicitly, using the --ndb-log-bin option; this is a change from previous versions of NDB Cluster, in which this option was enabled by default.

    Note

    You can also start the source with --binlog-format=MIXED, in which case row-based replication is used automatically when replicating between clusters. Statement-based binary logging is not supported for NDB Cluster Replication (see Section 23.6.2, “General Requirements for NDB Cluster Replication”).

  2. Start the MySQL replica server as shown here:

    shellR> mysqld --ndbcluster --server-id=id &
    

    In the command just shown, id is the replica server's unique ID. It is not necessary to enable logging on the replica.

    Note

    You should use the --skip-slave-start option with this command or else you should include skip-slave-start in the replica server's my.cnf file, unless you want replication to begin immediately. With the use of this option, the start of replication is delayed until the appropriate START REPLICA | SLAVE statement has been issued, as explained in Step 4 below.

  3. It is necessary to synchronize the replica server with the source server's replication binary log. If binary logging has not previously been running on the source, run the following statement on the replica:

    mysqlR> CHANGE MASTER TO
         -> MASTER_LOG_FILE='',
         -> MASTER_LOG_POS=4;
    

    This instructs the replica to begin reading the source server's binary log from the log's starting point. Otherwise—that is, if you are loading data from the source using a backup—see Section 23.6.8, “Implementing Failover with NDB Cluster Replication”, for information on how to obtain the correct values to use for MASTER_LOG_FILE and MASTER_LOG_POS in such cases.

  4. Finally, instruct the replica to begin applying replication by issuing this command from the mysql client on the replica:

    mysqlR> START SLAVE;
    Or from MySQL 8.0.22:
    mysqlR> START REPLICA;

    This also initiates the transmission of data and changes from the source to the replica.

It is also possible to use two replication channels, in a manner similar to the procedure described in the next section; the differences between this and using a single replication channel are covered in Section 23.6.7, “Using Two Replication Channels for NDB Cluster Replication”.

It is also possible to improve cluster replication performance by enabling batched updates. This can be accomplished by setting the slave_allow_batching system variable on the replicas' mysqld processes. Normally, updates are applied as soon as they are received. However, the use of batching causes updates to be applied in batches of 32 KB each; this can result in higher throughput and less CPU usage, particularly where individual updates are relatively small.

Note

Batching works on a per-epoch basis; updates belonging to more than one transaction can be sent as part of the same batch.

All outstanding updates are applied when the end of an epoch is reached, even if the updates total less than 32 KB.

Batching can be turned on and off at runtime. To activate it at runtime, you can use either of these two statements:

SET GLOBAL slave_allow_batching = 1;
SET GLOBAL slave_allow_batching = ON;

If a particular batch causes problems (such as a statement whose effects do not appear to be replicated correctly), batching can be deactivated using either of the following statements:

SET GLOBAL slave_allow_batching = 0;
SET GLOBAL slave_allow_batching = OFF;

You can check whether batching is currently being used by means of an appropriate SHOW VARIABLES statement, like this one:

mysql> SHOW VARIABLES LIKE 'slave%';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| slave_allow_batching      | ON    |
| slave_compressed_protocol | OFF   |
| slave_load_tmpdir         | /tmp  |
| slave_net_timeout         | 3600  |
| slave_skip_errors         | OFF   |
| slave_transaction_retries | 10    |
+---------------------------+-------+
6 rows in set (0.00 sec)

23.6.7 Using Two Replication Channels for NDB Cluster Replication

In a more complete example scenario, we envision two replication channels to provide redundancy and thereby guard against possible failure of a single replication channel. This requires a total of four replication servers, two source servers on the source cluster and two replica servers on the replica cluster. For purposes of the discussion that follows, we assume that unique identifiers are assigned as shown here:

Table 23.69 NDB Cluster replication servers described in the text

Server ID Description
1 Source - primary replication channel (S)
2 Source - secondary replication channel (S')
3 Replica - primary replication channel (R)
4 replica - secondary replication channel (R')

Setting up replication with two channels is not radically different from setting up a single replication channel. First, the mysqld processes for the primary and secondary replication source servers must be started, followed by those for the primary and secondary replicas. The replication processes can be initiated by issuing the START REPLICA | SLAVE statement on each of the replicas. The commands and the order in which they need to be issued are shown here:

  1. Start the primary replication source:

    shellS> mysqld --ndbcluster --server-id=1 \
                   --log-bin &
    
  2. Start the secondary replication source:

    shellS'> mysqld --ndbcluster --server-id=2 \
                   --log-bin &
    
  3. Start the primary replica server:

    shellR> mysqld --ndbcluster --server-id=3 \
                   --skip-slave-start &
    
  4. Start the secondary replica server:

    shellR'> mysqld --ndbcluster --server-id=4 \
                    --skip-slave-start &
    
  5. Finally, initiate replication on the primary channel by executing the START REPLICA | SLAVE statement on the primary replica as shown here:

    mysqlR> START SLAVE;
    Or from MySQL 8.0.22:
    mysqlR> START REPLICA;
    
    Warning

    Only the primary channel must be started at this point. The secondary replication channel needs to be started only in the event that the primary replication channel fails, as described in Section 23.6.8, “Implementing Failover with NDB Cluster Replication”. Running multiple replication channels simultaneously can result in unwanted duplicate records being created on the replicas.

As mentioned previously, it is not necessary to enable binary logging on the replicas.

23.6.8 Implementing Failover with NDB Cluster Replication

In the event that the primary Cluster replication process fails, it is possible to switch over to the secondary replication channel. The following procedure describes the steps required to accomplish this.

  1. Obtain the time of the most recent global checkpoint (GCP). That is, you need to determine the most recent epoch from the ndb_apply_status table on the replica cluster, which can be found using the following query:

    mysqlR'> SELECT @latest:=MAX(epoch)
          ->        FROM mysql.ndb_apply_status;
    

    In a circular replication topology, with a source and a replica running on each host, when you are using ndb_log_apply_status=1, NDB Cluster epochs are written in the replicas' binary logs. This means that the ndb_apply_status table contains information for the replica on this host as well as for any other host which acts as a replica of the replication source server running on this host.

    In this case, you need to determine the latest epoch on this replica to the exclusion of any epochs from any other replicas in this replica's binary log that were not listed in the IGNORE_SERVER_IDS options of the CHANGE MASTER TO statement used to set up this replica. The reason for excluding such epochs is that rows in the mysql.ndb_apply_status table whose server IDs have a match in the IGNORE_SERVER_IDS list from the CHANGE MASTER TO statement used to prepare this replicas's source are also considered to be from local servers, in addition to those having the replica's own server ID. You can retrieve this list as Replicate_Ignore_Server_Ids from the output of SHOW REPLICA | SLAVE STATUS. We assume that you have obtained this list and are substituting it for ignore_server_ids in the query shown here, which like the previous version of the query, selects the greatest epoch into a variable named @latest:

    mysqlR'> SELECT @latest:=MAX(epoch)
          ->        FROM mysql.ndb_apply_status
          ->        WHERE server_id NOT IN (ignore_server_ids);
    

    In some cases, it may be simpler or more efficient (or both) to use a list of the server IDs to be included and server_id IN server_id_list in the WHERE condition of the preceding query.

  2. Using the information obtained from the query shown in Step 1, obtain the corresponding records from the ndb_binlog_index table on the source cluster.

    You can use the following query to obtain the needed records from the ndb_binlog_index table on the source:

    mysqlS'> SELECT
          ->     @file:=SUBSTRING_INDEX(next_file, '/', -1),
          ->     @pos:=next_position
          -> FROM mysql.ndb_binlog_index
          -> WHERE epoch >= @latest
          -> ORDER BY epoch ASC LIMIT 1;
    

    These are the records saved on the source since the failure of the primary replication channel. We have employed a user variable @latest here to represent the value obtained in Step 1. Of course, it is not possible for one mysqld instance to access user variables set on another server instance directly. These values must be plugged in to the second query manually or by an application.

    Important

    You must ensure that the replica mysqld is started with --slave-skip-errors=ddl_exist_errors before executing START REPLICA | SLAVE. Otherwise, replication may stop with duplicate DDL errors.

  3. Now it is possible to synchronize the secondary channel by running the following query on the secondary replica server:

    mysqlR'> CHANGE MASTER TO
          ->     MASTER_LOG_FILE='@file',
          ->     MASTER_LOG_POS=@pos;
    

    Again we have employed user variables (in this case @file and @pos) to represent the values obtained in Step 2 and applied in Step 3; in practice these values must be inserted manually or using an application that can access both of the servers involved.

    Note

    @file is a string value such as '/var/log/mysql/replication-source-bin.00001', and so must be quoted when used in SQL or application code. However, the value represented by @pos must not be quoted. Although MySQL normally attempts to convert strings to numbers, this case is an exception.

  4. You can now initiate replication on the secondary channel by issuing the appropriate command on the secondary replica mysqld:

    mysqlR'> START SLAVE;
    Or from MySQL 8.0.22:
    mysqlR'> START REPLICA;

Once the secondary replication channel is active, you can investigate the failure of the primary and effect repairs. The precise actions required to do this depend upon the reasons for which the primary channel failed.

Warning

The secondary replication channel is to be started only if and when the primary replication channel has failed. Running multiple replication channels simultaneously can result in unwanted duplicate records being created on the replicas.

If the failure is limited to a single server, it should in theory be possible to replicate from S to R', or from S' to R.

23.6.9 NDB Cluster Backups With NDB Cluster Replication

This section discusses making backups and restoring from them using NDB Cluster replication. We assume that the replication servers have already been configured as covered previously (see Section 23.6.5, “Preparing the NDB Cluster for Replication”, and the sections immediately following). This having been done, the procedure for making a backup and then restoring from it is as follows:

  1. There are two different methods by which the backup may be started.

    • Method A.  This method requires that the cluster backup process was previously enabled on the source server, prior to starting the replication process. This can be done by including the following line in a [mysql_cluster] section in the my.cnf file, where management_host is the IP address or host name of the NDB management server for the source cluster, and port is the management server's port number:

      ndb-connectstring=management_host[:port]
      
      Note

      The port number needs to be specified only if the default port (1186) is not being used. See Section 23.2.3, “Initial Configuration of NDB Cluster”, for more information about ports and port allocation in NDB Cluster.

      In this case, the backup can be started by executing this statement on the replication source:

      shellS> ndb_mgm -e "START BACKUP"
      
    • Method B.  If the my.cnf file does not specify where to find the management host, you can start the backup process by passing this information to the NDB management client as part of the START BACKUP command. This can be done as shown here, where management_host and port are the host name and port number of the management server:

      shellS> ndb_mgm management_host:port -e "START BACKUP"
      

      In our scenario as outlined earlier (see Section 23.6.5, “Preparing the NDB Cluster for Replication”), this would be executed as follows:

      shellS> ndb_mgm rep-source:1186 -e "START BACKUP"
      
  2. Copy the cluster backup files to the replica that is being brought on line. Each system running an ndbd process for the source cluster has cluster backup files located on it, and all of these files must be copied to the replica to ensure a successful restore. The backup files can be copied into any directory on the computer where the replica's management host resides, as long as the MySQL and NDB binaries have read permissions in that directory. In this case, we assume that these files have been copied into the directory /var/BACKUPS/BACKUP-1.

    While it is not necessary that the replica cluster have the same number of ndbd processes (data nodes) as the source, it is highly recommended this number be the same. It is necessary that the replica be started with the --skip-slave-start option, to prevent premature startup of the replication process.

  3. Create any databases on the replica cluster that are present on the source cluster and that are to be replicated.

    Important

    A CREATE DATABASE (or CREATE SCHEMA) statement corresponding to each database to be replicated must be executed on each SQL node in the replica cluster.

  4. Reset the replica cluster using this statement in the mysql client:

    mysqlR> RESET SLAVE;
    Or from MySQL 8.0.22:
    mysqlR> RESET REPLICA;
    
  5. You can now start the cluster restoration process on the replica using the ndb_restore command for each backup file in turn. For the first of these, it is necessary to include the -m option to restore the cluster metadata, as shown here:

    shellR> ndb_restore -c replica_host:port -n node-id \
            -b backup-id -m -r dir
    

    dir is the path to the directory where the backup files have been placed on the replica. For the ndb_restore commands corresponding to the remaining backup files, the -m option should not be used.

    For restoring from a source cluster with four data nodes (as shown in the figure in Section 23.6, “NDB Cluster Replication”) where the backup files have been copied to the directory /var/BACKUPS/BACKUP-1, the proper sequence of commands to be executed on the replica might look like this:

    shellR> ndb_restore -c replica-host:1186 -n 2 -b 1 -m \
            -r ./var/BACKUPS/BACKUP-1
    shellR> ndb_restore -c replica-host:1186 -n 3 -b 1 \
            -r ./var/BACKUPS/BACKUP-1
    shellR> ndb_restore -c replica-host:1186 -n 4 -b 1 \
            -r ./var/BACKUPS/BACKUP-1
    shellR> ndb_restore -c replica-host:1186 -n 5 -b 1 -e \
            -r ./var/BACKUPS/BACKUP-1
    
    Important

    The -e (or --restore-epoch) option in the final invocation of ndb_restore in this example is required to make sure that the epoch is written to the replica's mysql.ndb_apply_status table. Without this information, the replica cannot synchronize properly with the source. (See Section 23.4.23, “ndb_restore — Restore an NDB Cluster Backup”.)

  6. Now you need to obtain the most recent epoch from the ndb_apply_status table on the replica (as discussed in Section 23.6.8, “Implementing Failover with NDB Cluster Replication”):

    mysqlR> SELECT @latest:=MAX(epoch)
            FROM mysql.ndb_apply_status;
    
  7. Using @latest as the epoch value obtained in the previous step, you can obtain the correct starting position @pos in the correct binary log file @file from the mysql.ndb_binlog_index table on the source using the query shown here:

    mysqlS> SELECT
         ->     @file:=SUBSTRING_INDEX(File, '/', -1),
         ->     @pos:=Position
         -> FROM mysql.ndb_binlog_index
         -> WHERE epoch >= @latest
         -> ORDER BY epoch ASC LIMIT 1;
    

    In the event that there is currently no replication traffic, you can get this information by running SHOW MASTER STATUS on the source and using the value shown in the Position column of the output for the file whose name has the suffix with the greatest value for all files shown in the File column. In this case, you must determine which file this is and supply the name in the next step manually or by parsing the output with a script.

  8. Using the values obtained in the previous step, you can now issue the appropriate CHANGE MASTER TO statement in the replica's mysql client:

    mysqlR> CHANGE MASTER TO
         ->     MASTER_LOG_FILE='@file',
         ->     MASTER_LOG_POS=@pos;
    
  9. Now that the replica knows from what point in which binary log file to start reading data from the source, you can cause the replica to begin replicating with this statement:

    mysqlR> START SLAVE;
    Or from MySQL 8.0.22:
    mysqlR> START REPLICA;

To perform a backup and restore on a second replication channel, it is necessary only to repeat these steps, substituting the host names and IDs of the secondary source and replica for those of the primary source and replica servers where appropriate, and running the preceding statements on them.

For additional information on performing Cluster backups and restoring Cluster from backups, see Section 23.5.8, “Online Backup of NDB Cluster”.

23.6.9.1 NDB Cluster Replication: Automating Synchronization of the Replica to the Source Binary Log

It is possible to automate much of the process described in the previous section (see Section 23.6.9, “NDB Cluster Backups With NDB Cluster Replication”). The following Perl script reset-replica.pl serves as an example of how you can do this.

#!/user/bin/perl -w

#  file: reset-replica.pl

#  Copyright (c) 2005, 2020, Oracle and/or its affiliates. All rights reserved.

#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.

#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.

#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to:
#  Free Software Foundation, Inc.
#  59 Temple Place, Suite 330
#  Boston, MA 02111-1307 USA
#
#  Version 1.1


######################## Includes ###############################

use DBI;

######################## Globals ################################

my  $m_host='';
my  $m_port='';
my  $m_user='';
my  $m_pass='';
my  $s_host='';
my  $s_port='';
my  $s_user='';
my  $s_pass='';
my  $dbhM='';
my  $dbhS='';

####################### Sub Prototypes ##########################

sub CollectCommandPromptInfo;
sub ConnectToDatabases;
sub DisconnectFromDatabases;
sub GetReplicaEpoch;
sub GetSourceInfo;
sub UpdateReplica;

######################## Program Main ###########################

CollectCommandPromptInfo;
ConnectToDatabases;
GetReplicaEpoch;
GetSourceInfo;
UpdateReplica;
DisconnectFromDatabases;

################## Collect Command Prompt Info ##################

sub CollectCommandPromptInfo
{
  ### Check that user has supplied correct number of command line args
  die "Usage:\n
       reset-replica >source MySQL host< >source MySQL port< \n
                   >source user< >source pass< >replica MySQL host< \n
                   >replica MySQL port< >replica user< >replica pass< \n
       All 8 arguments must be passed. Use BLANK for NULL passwords\n"
       unless @ARGV == 8;

  $m_host  =  $ARGV[0];
  $m_port  =  $ARGV[1];
  $m_user  =  $ARGV[2];
  $m_pass  =  $ARGV[3];
  $s_host  =  $ARGV[4];
  $s_port  =  $ARGV[5];
  $s_user  =  $ARGV[6];
  $s_pass  =  $ARGV[7];

  if ($m_pass eq "BLANK") { $m_pass = '';}
  if ($s_pass eq "BLANK") { $s_pass = '';}
}

###############  Make connections to both databases #############

sub ConnectToDatabases
{
  ### Connect to both source and replica cluster databases

  ### Connect to source
  $dbhM
    = DBI->connect(
    "dbi:mysql:database=mysql;host=$m_host;port=$m_port",
    "$m_user", "$m_pass")
      or die "Can't connect to source cluster MySQL process!
              Error: $DBI::errstr\n";

  ### Connect to replica
  $dbhS
    = DBI->connect(
          "dbi:mysql:database=mysql;host=$s_host",
          "$s_user", "$s_pass")
    or die "Can't connect to replica cluster MySQL process!
            Error: $DBI::errstr\n";
}

################  Disconnect from both databases ################

sub DisconnectFromDatabases
{
  ### Disconnect from source

  $dbhM->disconnect
  or warn " Disconnection failed: $DBI::errstr\n";

  ### Disconnect from replica

  $dbhS->disconnect
  or warn " Disconnection failed: $DBI::errstr\n";
}

######################  Find the last good GCI ##################

sub GetReplicaEpoch
{
  $sth = $dbhS->prepare("SELECT MAX(epoch)
                         FROM mysql.ndb_apply_status;")
      or die "Error while preparing to select epoch from replica: ",
             $dbhS->errstr;

  $sth->execute
      or die "Selecting epoch from replica error: ", $sth->errstr;

  $sth->bind_col (1, \$epoch);
  $sth->fetch;
  print "\tReplica epoch =  $epoch\n";
  $sth->finish;
}

#######  Find the position of the last GCI in the binary log ########

sub GetSourceInfo
{
  $sth = $dbhM->prepare("SELECT
                           SUBSTRING_INDEX(File, '/', -1), Position
                         FROM mysql.ndb_binlog_index
                         WHERE epoch > $epoch
                         ORDER BY epoch ASC LIMIT 1;")
      or die "Prepare to select from source error: ", $dbhM->errstr;

  $sth->execute
      or die "Selecting from source error: ", $sth->errstr;

  $sth->bind_col (1, \$binlog);
  $sth->bind_col (2, \$binpos);
  $sth->fetch;
  print "\tSource binary log file =  $binlog\n";
  print "\tSource binary log position =  $binpos\n";
  $sth->finish;
}

##########  Set the replica to process from that location #########

sub UpdateReplica
{
  $sth = $dbhS->prepare("CHANGE MASTER TO
                         MASTER_LOG_FILE='$binlog',
                         MASTER_LOG_POS=$binpos;")
      or die "Prepare to CHANGE MASTER error: ", $dbhS->errstr;

  $sth->execute
       or die "CHANGE MASTER on replica error: ", $sth->errstr;
  $sth->finish;
  print "\tReplica has been updated. You may now start the replica.\n";
}

# end reset-replica.pl

23.6.9.2 Point-In-Time Recovery Using NDB Cluster Replication

Point-in-time recovery—that is, recovery of data changes made since a given point in time—is performed after restoring a full backup that returns the server to its state when the backup was made. Performing point-in-time recovery of NDB Cluster tables with NDB Cluster and NDB Cluster Replication can be accomplished using a native NDB data backup (taken by issuing CREATE BACKUP in the ndb_mgm client) and restoring the ndb_binlog_index table (from a dump made using mysqldump).

To perform point-in-time recovery of NDB Cluster, it is necessary to follow the steps shown here:

  1. Back up all NDB databases in the cluster, using the START BACKUP command in the ndb_mgm client (see Section 23.5.8, “Online Backup of NDB Cluster”).

  2. At some later point, prior to restoring the cluster, make a backup of the mysql.ndb_binlog_index table. It is probably simplest to use mysqldump for this task. Also back up the binary log files at this time.

    This backup should be updated regularly—perhaps even hourly—depending on your needs.

  3. (Catastrophic failure or error occurs.)

  4. Locate the last known good backup.

  5. Clear the data node file systems (using ndbd --initial or ndbmtd --initial).

    Note

    Beginning with NDB 8.0.21, Disk Data tablespace and log files are removed by --initial. Previously, it was necessary to delete these manually.

  6. Use DROP TABLE or TRUNCATE TABLE with the mysql.ndb_binlog_index table.

  7. Execute ndb_restore, restoring all data. You must include the --restore-epoch option when you run ndb_restore, so that the ndb_apply_status table is populated correctly. (See Section 23.4.23, “ndb_restore — Restore an NDB Cluster Backup”, for more information.)

  8. Restore the ndb_binlog_index table from the output of mysqldump and restore the binary log files from backup, if necessary.

  9. Find the epoch applied most recently—that is, the maximum epoch column value in the ndb_apply_status table—as the user variable @LATEST_EPOCH (emphasized):

    SELECT @LATEST_EPOCH:=MAX(epoch)
        FROM mysql.ndb_apply_status;
    
  10. Find the latest binary log file (@FIRST_FILE) and position (Position column value) within this file that correspond to @LATEST_EPOCH in the ndb_binlog_index table:

    SELECT Position, @FIRST_FILE:=File
        FROM mysql.ndb_binlog_index
        WHERE epoch > @LATEST_EPOCH ORDER BY epoch ASC LIMIT 1;
    
  11. Using mysqlbinlog, replay the binary log events from the given file and position up to the point of the failure. (See Section 4.6.8, “mysqlbinlog — Utility for Processing Binary Log Files”.)

See also Section 7.5, “Point-in-Time (Incremental) Recovery”, for more information about the binary log, replication, and incremental recovery.

23.6.10 NDB Cluster Replication: Bidrectional and Circular Replication

It is possible to use NDB Cluster for bidirectional replication between two clusters, as well as for circular replication between any number of clusters.

Circular replication example.  In the next few paragraphs we consider the example of a replication setup involving three NDB Clusters numbered 1, 2, and 3, in which Cluster 1 acts as the replication source for Cluster 2, Cluster 2 acts as the source for Cluster 3, and Cluster 3 acts as the source for Cluster 1. Each cluster has two SQL nodes, with SQL nodes A and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and SQL nodes E and F belonging to Cluster 3.

Circular replication using these clusters is supported as long as the following conditions are met:

  • The SQL nodes on all sources and replicas are the same.

  • All SQL nodes acting as sources and replicas are started with the log_slave_updates system variable enabled.

This type of circular replication setup is shown in the following diagram:

Figure 23.36 NDB Cluster Circular Replication with All Sources As Replicas

Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that all sources are also replicas.

In this scenario, SQL node A in Cluster 1 replicates to SQL node C in Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E replicates to SQL node A. In other words, the replication line (indicated by the curved arrows in the diagram) directly connects all SQL nodes used as replication sources and replicas.

It is also possible to set up circular replication in such a way that not all source SQL nodes are also replicas, as shown here:

Figure 23.37 NDB Cluster Circular Replication Where Not All Sources Are Replicas

Some content is described in the surrounding text. The diagram shows three clusters, each with two nodes. Arrows connecting SQL nodes in different clusters illustrate that not all sources are replicas.

In this case, different SQL nodes in each cluster are used as replication sources and replicas. You must not start any of the SQL nodes with the log_slave_updates system variable enabled. This type of circular replication scheme for NDB Cluster, in which the line of replication (again indicated by the curved arrows in the diagram) is discontinuous, should be possible, but it should be noted that it has not yet been thoroughly tested and must therefore still be considered experimental.

Using NDB-native backup and restore to initialize a replica cluster.  When setting up circular replication, it is possible to initialize the replica cluster by using the management client START BACKUP command on one NDB Cluster to create a backup and then applying this backup on another NDB Cluster using ndb_restore. This does not automatically create binary logs on the second NDB Cluster's SQL node acting as the replica; in order to cause the binary logs to be created, you must issue a SHOW TABLES statement on that SQL node; this should be done prior to running START REPLICA | SLAVE. This is a known issue.

Multi-source failover example.  In this section, we discuss failover in a multi-source NDB Cluster replication setup with three NDB Clusters having server IDs 1, 2, and 3. In this scenario, Cluster 1 replicates to Clusters 2 and 3; Cluster 2 also replicates to Cluster 3. This relationship is shown here:

Figure 23.38 NDB Cluster Multi-Master Replication With 3 Sources

Multi-source NDB Cluster replication setup with three NDB Clusters having server IDs 1, 2, and 3; Cluster 1 replicates to Clusters 2 and 3; Cluster 2 also replicates to Cluster 3.

In other words, data replicates from Cluster 1 to Cluster 3 through 2 different routes: directly, and by way of Cluster 2.

Not all MySQL servers taking part in multi-source replication must act as both source and replica, and a given NDB Cluster might use different SQL nodes for different replication channels. Such a case is shown here:

Figure 23.39 NDB Cluster Multi-Source Replication, With MySQL Servers

Concepts are described in the surrounding text. Shows three nodes: SQL node A in Cluster 1 replicates to SQL node F in Cluster 3; SQL node B in Cluster 1 replicates to SQL node C in Cluster 2; SQL node E in Cluster 3 replicates to SQL node G in Cluster 3. SQL nodes A and B in cluster 1 have --log-slave-updates=0; SQL nodes C in Cluster 2, and SQL nodes F and G in Cluster 3 have --log-slave-updates=1; and SQL nodes D and E in Cluster 2 have --log-slave-updates=0.

MySQL servers acting as replicas must be run with the log_slave_updates system variable enabled. Which mysqld processes require this option is also shown in the preceding diagram.

Note

Using the log_slave_updates system variable has no effect on servers not being run as replicas.

The need for failover arises when one of the replicating clusters goes down. In this example, we consider the case where Cluster 1 is lost to service, and so Cluster 3 loses 2 sources of updates from Cluster 1. Because replication between NDB Clusters is asynchronous, there is no guarantee that Cluster 3's updates originating directly from Cluster 1 are more recent than those received through Cluster 2. You can handle this by ensuring that Cluster 3 catches up to Cluster 2 with regard to updates from Cluster 1. In terms of MySQL servers, this means that you need to replicate any outstanding updates from MySQL server C to server F.

On server C, perform the following queries:

mysqlC> SELECT @latest:=MAX(epoch)
     ->     FROM mysql.ndb_apply_status
     ->     WHERE server_id=1;

mysqlC> SELECT
     ->     @file:=SUBSTRING_INDEX(File, '/', -1),
     ->     @pos:=Position
     ->     FROM mysql.ndb_binlog_index
     ->     WHERE orig_epoch >= @latest
     ->     AND orig_server_id = 1
     ->     ORDER BY epoch ASC LIMIT 1;
Note

You can improve the performance of this query, and thus likely speed up failover times significantly, by adding the appropriate index to the ndb_binlog_index table. See Section 23.6.4, “NDB Cluster Replication Schema and Tables”, for more information.

Copy over the values for @file and @pos manually from server C to server F (or have your application perform the equivalent). Then, on server F, execute the following CHANGE MASTER TO statement:

mysqlF> CHANGE MASTER TO
     ->     MASTER_HOST = 'serverC'
     ->     MASTER_LOG_FILE='@file',
     ->     MASTER_LOG_POS=@pos;

Once this has been done, you can issue a START REPLICA | SLAVE statement on MySQL server F; this causes any missing updates originating from server B to be replicated to server F.

The CHANGE MASTER TO statement also supports an IGNORE_SERVER_IDS option which takes a comma-separated list of server IDs and causes events originating from the corresponding servers to be ignored. For more information, see Section 13.4.2.1, “CHANGE MASTER TO Statement”, and Section 13.7.7.36, “SHOW SLAVE | REPLICA STATUS Statement”. For information about how this option intereacts with the ndb_log_apply_status variable, see Section 23.6.8, “Implementing Failover with NDB Cluster Replication”.

23.6.11 NDB Cluster Replication Conflict Resolution

When using a replication setup involving multiple sources (including circular replication), it is possible that different sources may try to update the same row on the replica with different data. Conflict resolution in NDB Cluster Replication provides a means of resolving such conflicts by permitting a user-defined resolution column to be used to determine whether or not an update on a given source should be applied on the replica.

Some types of conflict resolution supported by NDB Cluster (NDB$OLD(), NDB$MAX(), NDB$MAX_DELETE_WIN()) implement this user-defined column as a timestamp column (although its type cannot be TIMESTAMP, as explained later in this section). These types of conflict resolution are always applied a row-by-row basis rather than a transactional basis. The epoch-based conflict resolution functions NDB$EPOCH() and NDB$EPOCH_TRANS() compare the order in which epochs are replicated (and thus these functions are transactional). Different methods can be used to compare resolution column values on the replica when conflicts occur, as explained later in this section; the method used can be set on a per-table basis.

You should also keep in mind that it is the application's responsibility to ensure that the resolution column is correctly populated with relevant values, so that the resolution function can make the appropriate choice when determining whether to apply an update.

Requirements.  Preparations for conflict resolution must be made on both the source and the replica. These tasks are described in the following list:

  • On the source writing the binary logs, you must determine which columns are sent (all columns or only those that have been updated). This is done for the MySQL Server as a whole by applying the mysqld startup option --ndb-log-updated-only (described later in this section) or on a per-table basis by entries in the mysql.ndb_replication table (see The ndb_replication system table).

    Note

    If you are replicating tables with very large columns (such as TEXT or BLOB columns), --ndb-log-updated-only can also be useful for reducing the size of the binary logs and avoiding possible replication failures due to exceeding max_allowed_packet.

    See Section 17.5.1.20, “Replication and max_allowed_packet”, for more information about this issue.

  • On the replica, you must determine which type of conflict resolution to apply (latest timestamp wins, same timestamp wins, primary wins, primary wins, complete transaction, or none). This is done using the mysql.ndb_replication system table, on a per-table basis (see The ndb_replication system table).

  • NDB Cluster also supports read conflict detection, that is, detecting conflicts between reads of a given row in one cluster and updates or deletes of the same row in another cluster. This requires exclusive read locks obtained by setting ndb_log_exclusive_reads equal to 1 on the replica. All rows read by a conflicting read are logged in the exceptions table. For more information, see Read conflict detection and resolution.

When using the functions NDB$OLD(), NDB$MAX(), and NDB$MAX_DELETE_WIN() for timestamp-based conflict resolution, we often refer to the column used for determining updates as a timestamp column. However, the data type of this column is never TIMESTAMP; instead, its data type should be INT (INTEGER) or BIGINT. The timestamp column should also be UNSIGNED and NOT NULL.

The NDB$EPOCH() and NDB$EPOCH_TRANS() functions discussed later in this section work by comparing the relative order of replication epochs applied on a primary and secondary NDB Cluster, and do not make use of timestamps.

Source column control.  We can see update operations in terms of before and after images—that is, the states of the table before and after the update is applied. Normally, when updating a table with a primary key, the before image is not of great interest; however, when we need to determine on a per-update basis whether or not to use the updated values on a replica, we need to make sure that both images are written to the source's binary log. This is done with the --ndb-log-update-as-write option for mysqld, as described later in this section.

Important

Whether logging of complete rows or of updated columns only is done is decided when the MySQL server is started, and cannot be changed online; you must either restart mysqld, or start a new mysqld instance with different logging options.

Logging Full or Partial Rows (--ndb-log-updated-only Option)

Command-Line Format --ndb-log-updated-only[={OFF|ON}]
System Variable ndb_log_updated_only
Scope Global
Dynamic Yes
SET_VAR Hint Applies No
Type Boolean
Default Value ON

For purposes of conflict resolution, there are two basic methods of logging rows, as determined by the setting of the --ndb-log-updated-only option for mysqld:

  • Log complete rows

  • Log only column data that has been updated—that is, column data whose value has been set, regardless of whether or not this value was actually changed. This is the default behavior.

It is usually sufficient—and more efficient—to log updated columns only; however, if you need to log full rows, you can do so by setting --ndb-log-updated-only to 0 or OFF.

--ndb-log-update-as-write Option: Logging Changed Data as Updates

Command-Line Format --ndb-log-update-as-write[={OFF|ON}]
System Variable ndb_log_update_as_write
Scope Global
Dynamic Yes
SET_VAR Hint Applies No
Type Boolean
Default Value ON

The setting of the MySQL Server's --ndb-log-update-as-write option determines whether logging is performed with or without the before image. Because conflict resolution is done in the MySQL Server's update handler, it is necessary to control logging performed by the replication source such that updates are updates and not writes; that is, such that updates are treated as changes in existing rows rather than the writing of new rows, even though these replace existing rows. This option is turned on by default; in other words, updates are treated as writes. That is, updates are by default written as write_row events in the binary log, rather than as update_row events.

To disable the option, start the source mysqld with --ndb-log-update-as-write=0 or --ndb-log-update-as-write=OFF. You must do this when replicating from NDB tables to tables using a different storage engine; see Replication from NDB to other storage engines, and Replication from NDB to a nontransactional storage engine, for more information.

Conflict resolution control.  Conflict resolution is usually enabled on the server where conflicts can occur. Like logging method selection, it is enabled by entries in the mysql.ndb_replication table.

The ndb_replication system table.  To enable conflict resolution, it is necessary to create an ndb_replication table in the mysql system database on the source, the replica, or both, depending on the conflict resolution type and method to be employed. This table is used to control logging and conflict resolution functions on a per-table basis, and has one row per table involved in replication. ndb_replication is created and filled with control information on the server where the conflict is to be resolved. In a simple source-replica setup where data can also be changed locally on the replica this is typically the replica. In a more complex replication scheme, such as bidirectional replication, this is usually all of the sources involved. Each row in mysql.ndb_replication corresponds to a table being replicated, and specifies how to log and resolve conflicts (that is, which conflict resolution function, if any, to use) for that table. The definition of the mysql.ndb_replication table is shown here:

CREATE TABLE mysql.ndb_replication  (
    db VARBINARY(63),
    table_name VARBINARY(63),
    server_id INT UNSIGNED,
    binlog_type INT UNSIGNED,
    conflict_fn VARBINARY(128),
    PRIMARY KEY USING HASH (db, table_name, server_id)
)   ENGINE=NDB
PARTITION BY KEY(db,table_name);

The columns in this table are described in the next few paragraphs.

db.  The name of the database containing the table to be replicated. You may employ either or both of the wildcards _ and % as part of the database name. Matching is similar to what is implemented for the LIKE operator.

table_name.  The name of the table to be replicated. The table name may include either or both of the wildcards _ and %. Matching is similar to what is implemented for the LIKE operator.

server_id.  The unique server ID of the MySQL instance (SQL node) where the table resides.

binlog_type.  The type of binary logging to be employed. This is determined as shown in the following table:

Table 23.70 binlog_type values, with internal values and descriptions

Value Internal Value Description
0 NBT_DEFAULT Use server default
1 NBT_NO_LOGGING Do not log this table in the binary log
2 NBT_UPDATED_ONLY Only updated attributes are logged
3 NBT_FULL Log full row, even if not updated (MySQL server default behavior)
4 NBT_USE_UPDATE (For generating NBT_UPDATED_ONLY_USE_UPDATE and NBT_FULL_USE_UPDATE values only—not intended for separate use)
5 [Not used] ---
6 NBT_UPDATED_ONLY_USE_UPDATE (equal to NBT_UPDATED_ONLY | NBT_USE_UPDATE) Use updated attributes, even if values are unchanged
7 NBT_FULL_USE_UPDATE (equal to NBT_FULL | NBT_USE_UPDATE) Use full row, even if values are unchanged

conflict_fn.  The conflict resolution function to be applied. This function must be specified as one of those shown in the following list:

These functions are described in the next few paragraphs.

NDB$OLD(column_name).  If the value of column_name is the same on both the source and the replica, then the update is applied; otherwise, the update is not applied on the replica and an exception is written to the log. This is illustrated by the following pseudocode:

if (source_old_column_value == replica_current_column_value)
  apply_update();
else
  log_exception();

This function can be used for same value wins conflict resolution. This type of conflict resolution ensures that updates are not applied on the replica from the wrong source.

Important

The column value from the source's before image is used by this function.

NDB$MAX(column_name).  If the timestamp column value for a given row coming from the source is higher than that on the replica, it is applied; otherwise it is not applied on the replica. This is illustrated by the following pseudocode:

if (source_new_column_value > replica_current_column_value)
  apply_update();

This function can be used for greatest timestamp wins conflict resolution. This type of conflict resolution ensures that, in the event of a conflict, the version of the row that was most recently updated is the version that persists.

Important

The column value from the sources's after image is used by this function.

NDB$MAX_DELETE_WIN().  This is a variation on NDB$MAX(). Due to the fact that no timestamp is available for a delete operation, a delete using NDB$MAX() is in fact processed as NDB$OLD, but for some use cases, this is not optimal. For NDB$MAX_DELETE_WIN(), if the timestamp column value for a given row adding or updating an existing row coming from the source is higher than that on the replica, it is applied. However, delete operations are treated as always having the higher value. This is illustrated by the following pseudocode:

if ( (source_new_column_value > replica_current_column_value)
        ||
      operation.type == "delete")
  apply_update();

This function can be used for greatest timestamp, delete wins conflict resolution. This type of conflict resolution ensures that, in the event of a conflict, the version of the row that was deleted or (otherwise) most recently updated is the version that persists.

Note

As with NDB$MAX(), the column value from the source's after image is the value used by this function.

NDB$EPOCH() and NDB$EPOCH_TRANS().  The NDB$EPOCH() function tracks the order in which replicated epochs are applied on a replica cluster relative to changes originating on the replica. This relative ordering is used to determine whether changes originating on the replica are concurrent with any changes that originate locally, and are therefore potentially in conflict.

Most of what follows in the description of NDB$EPOCH() also applies to NDB$EPOCH_TRANS(). Any exceptions are noted in the text.

NDB$EPOCH() is asymmetric, operating on one NDB Cluster in a bidirectional replication configuration (sometimes referred to as active-active replication). We refer here to cluster on which it operates as the primary, and the other as the secondary. The replica on the primary is responsible for detecting and handling conflicts, while the replica on the secondary is not involved in any conflict detection or handling.

When the replica on the primary detects conflicts, it injects events into its own binary log to compensate for these; this ensures that the secondary NDB Cluster eventually realigns itself with the primary and so keeps the primary and secondary from diverging. This compensation and realignment mechanism requires that the primary NDB Cluster always wins any conflicts with the secondary—that is, that the primary's changes are always used rather than those from the secondary in event of a conflict. This primary always wins rule has the following implications:

  • Operations that change data, once committed on the primary, are fully persistent and are not undone or rolled back by conflict detection and resolution.

  • Data read from the primary is fully consistent. Any changes committed on the Primary (locally or from the replica) are not reverted later.

  • Operations that change data on the secondary may later be reverted if the primary determines that they are in conflict.

  • Individual rows read on the secondary are self-consistent at all times, each row always reflecting either a state committed by the secondary, or one committed by the primary.

  • Sets of rows read on the secondary may not necessarily be consistent at a given single point in time. For NDB$EPOCH_TRANS(), this is a transient state; for NDB$EPOCH(), it can be a persistent state.

  • Assuming a period of sufficient length without any conflicts, all data on the secondary NDB Cluster (eventually) becomes consistent with the primary's data.

NDB$EPOCH() and NDB$EPOCH_TRANS() do not require any user schema modifications, or application changes to provide conflict detection. However, careful thought must be given to the schema used, and the access patterns used, to verify that the complete system behaves within specified limits.

Each of the NDB$EPOCH() and NDB$EPOCH_TRANS() functions can take an optional parameter; this is the number of bits to use to represent the lower 32 bits of the epoch, and should be set to no less than the value calculated as shown here:

CEIL( LOG2( TimeBetweenGlobalCheckpoints / TimeBetweenEpochs ), 1)

For the default values of these configuration parameters (2000 and 100 milliseconds, respectively), this gives a value of 5 bits, so the default value (6) should be sufficient, unless other values are used for TimeBetweenGlobalCheckpoints, TimeBetweenEpochs, or both. A value that is too small can result in false positives, while one that is too large could lead to excessive wasted space in the database.

Both NDB$EPOCH() and NDB$EPOCH_TRANS() insert entries for conflicting rows into the relevant exceptions tables, provided that these tables have been defined according to the same exceptions table schema rules as described elsewhere in this section (see NDB$OLD(column_name)). You must create any exceptions table before creating the data table with which it is to be used.

As with the other conflict detection functions discussed in this section, NDB$EPOCH() and NDB$EPOCH_TRANS() are activated by including relevant entries in the mysql.ndb_replication table (see The ndb_replication system table). The roles of the primary and secondary NDB Clusters in this scenario are fully determined by mysql.ndb_replication table entries.

Because the conflict detection algorithms employed by NDB$EPOCH() and NDB$EPOCH_TRANS() are asymmetric, you must use different values for the server_id entries of the primary and secondary replicas.

A conflict between DELETE operations alone is not sufficient to trigger a conflict using NDB$EPOCH() or NDB$EPOCH_TRANS(), and the relative placement within epochs does not matter. (Bug #18459944)

Conflict detection status variables.  Several status variables can be used to monitor conflict detection. You can see how many rows have been found in conflict by NDB$EPOCH() since this replica was last restarted from the current value of the Ndb_conflict_fn_epoch system status variable.

Ndb_conflict_fn_epoch_trans provides the number of rows that have been found directly in conflict by NDB$EPOCH_TRANS(). Ndb_conflict_fn_epoch2 and Ndb_conflict_fn_epoch2_trans show the number of rows found in conflict by NDB$EPOCH2() and NDB$EPOCH2_TRANS(), respectively. The number of rows actually realigned, including those affected due to their membership in or dependency on the same transactions as other conflicting rows, is given by Ndb_conflict_trans_row_reject_count.

For more information, see Section 23.3.3.9.3, “NDB Cluster Status Variables”.

Limitations on NDB$EPOCH().  The following limitations currently apply when using NDB$EPOCH() to perform conflict detection:

  • Conflicts are detected using NDB Cluster epoch boundaries, with granularity proportional to TimeBetweenEpochs (default: 100 milliseconds). The minimum conflict window is the minimum time during which concurrent updates to the same data on both clusters always report a conflict. This is always a nonzero length of time, and is roughly proportional to 2 * (latency + queueing + TimeBetweenEpochs). This implies that—assuming the default for TimeBetweenEpochs and ignoring any latency between clusters (as well as any queuing delays)—the minimum conflict window size is approximately 200 milliseconds. This minimum window should be considered when looking at expected application race patterns.

  • Additional storage is required for tables using the NDB$EPOCH() and NDB$EPOCH_TRANS() functions; from 1 to 32 bits extra space per row is required, depending on the value passed to the function.

  • Conflicts between delete operations may result in divergence between the primary and secondary. When a row is deleted on both clusters concurrently, the conflict can be detected, but is not recorded, since the row is deleted. This means that further conflicts during the propagation of any subsequent realignment operations are not detected, which can lead to divergence.

    Deletes should be externally serialized, or routed to one cluster only. Alternatively, a separate row should be updated transactionally with such deletes and any inserts that follow them, so that conflicts can be tracked across row deletes. This may require changes in applications.

  • Only two NDB Clusters in a birectional active-active configuration are currently supported when using NDB$EPOCH() or NDB$EPOCH_TRANS() for conflict detection.

  • Tables having BLOB or TEXT columns are not currently supported with NDB$EPOCH() or NDB$EPOCH_TRANS().

NDB$EPOCH_TRANS().  NDB$EPOCH_TRANS() extends the NDB$EPOCH() function. Conflicts are detected and handled in the same way using the primary wins all rule (see NDB$EPOCH() and NDB$EPOCH_TRANS()) but with the extra condition that any other rows updated in the same transaction in which the conflict occurred are also regarded as being in conflict. In other words, where NDB$EPOCH() realigns individual conflicting rows on the secondary, NDB$EPOCH_TRANS() realigns conflicting transactions.

In addition, any transactions which are detectably dependent on a conflicting transaction are also regarded as being in conflict, these dependencies being determined by the contents of the secondary cluster's binary log. Since the binary log contains only data modification operations (inserts, updates, and deletes), only overlapping data modifications are used to determine dependencies between transactions.

NDB$EPOCH_TRANS() is subject to the same conditions and limitations as NDB$EPOCH(), and in addition requires that all transaction IDs are recorded in the secondary's binary log (the --ndb-log-transaction-id option), which adds a variable overhead (up to 13 bytes per row). The deprecated log_bin_use_v1_row_events system variable, which defaults to OFF, must not be set to ON with NDB$EPOCH_TRANS().

See NDB$EPOCH() and NDB$EPOCH_TRANS().

Status information.  A server status variable Ndb_conflict_fn_max provides a count of the number of times that a row was not applied on the current SQL node due to greatest timestamp wins conflict resolution since the last time that mysqld was started.

The number of times that a row was not applied as the result of same timestamp wins conflict resolution on a given mysqld since the last time it was restarted is given by the global status variable Ndb_conflict_fn_old. In addition to incrementing Ndb_conflict_fn_old, the primary key of the row that was not used is inserted into an exceptions table, as explained later in this section.

NDB$EPOCH2().  The NDB$EPOCH2() function is similar to NDB$EPOCH(), except that NDB$EPOCH2() provides for delete-delete handling with a bidirectional replication topology. In this scenario, primary and secondary roles are assigned to the two sources by setting the ndb_slave_conflict_role system variable to the appropriate value on each source (usually one each of PRIMARY, SECONDARY). When this is done, modifications made by the secondary are reflected by the primary back to the secondary which then conditionally applies them.

NDB$EPOCH2_TRANS().  NDB$EPOCH2_TRANS() extends the NDB$EPOCH2() function. Conflicts are detected and handled in the same way, and assigning primary and secondary roles to the replicating clusters, but with the extra condition that any other rows updated in the same transaction in which the conflict occurred are also regarded as being in conflict. That is, NDB$EPOCH2() realigns individual conflicting rows on the secondary, while NDB$EPOCH_TRANS() realigns conflicting transactions.

Where NDB$EPOCH() and NDB$EPOCH_TRANS() use metadata that is specified per row, per last modified epoch, to determine on the primary whether an incoming replicated row change from the secondary is concurrent with a locally committed change; concurrent changes are regarded as conflicting, with subesequent exceptions table updates and realignment of the secondary. A problem arises when a row is deleted on the primary so there is no longer any last-modified epoch available to determine whether any replicated operations conflict, which means that conflicting delete operationss are not detected. This can result in divergence, an example being a delete on one cluster which is concurrent with a delete and insert on the other; this why delete operations can be routed to only one cluster when using NDB$EPOCH() and NDB$EPOCH_TRANS().

NDB$EPOCH2() bypasses the issue just described—storing information about deleted rows on the PRIMARY—by ignoring any delete-delete conflict, and by avoiding any potential resultant divergence as well. This is accomplished by reflecting any operation successfully applied on and replicated from the secondary back to the secondary. On its return to the secondary, it can be used to reapply an operation on the secondary which was deleted by an operation originating from the primary.

When using NDB$EPOCH2(), you should keep in mind that the secondary applies the delete from the primary, removing the new row until it is restored by a reflected operation. In theory, the subsequent insert or update on the secondary conflicts with the delete from the primary, but in this case, we choose to ignore this and allow the secondary to win, in the interest of preventing divergence between the clusters. In other words, after a delete, the primary does not detect conflicts, and instead adopts the secondary's following changes immediately. Because of this, the secondary's state can revisit multiple previous committed states as it progresses to a final (stable) state, and some of these may be visible.

You should also be aware that reflecting all operations from the secondary back to the primary increases the size of the primary's logbinary log, as well as demands on bandwidth, CPU usage, and disk I/O.

Application of reflected operations on the secondary depends on the state of the target row on the secondary. Whether or not reflected changes are applied on the secondary can be tracked by checking the Ndb_conflict_reflected_op_prepare_count and Ndb_conflict_reflected_op_discard_count status variables. The number of changes applied is simply the difference between these two values (note that Ndb_conflict_reflected_op_prepare_count is always greater than or equal to Ndb_conflict_reflected_op_discard_count).

Events are applied if and only if both of the following conditions are true:

  • The existence of the row—that is, whether or not it exists—is in accordance with the type of event. For delete and update operations, the row must already exist. For insert operations, the row must not exist.

  • The row was last modified by the primary. It is possible that the modification was accomplished through the execution of a reflected operation.

If both of the conditions are not met, the reflected operation is discarded by the secondary.

Conflict resolution exceptions table.  To use the NDB$OLD() conflict resolution function, it is also necessary to create an exceptions table corresponding to each NDB table for which this type of conflict resolution is to be employed. This is also true when using NDB$EPOCH() or NDB$EPOCH_TRANS(). The name of this table is that of the table for which conflict resolution is to be applied, with the string $EX appended. (For example, if the name of the original table is mytable, the name of the corresponding exceptions table name should be mytable$EX.) The syntax for creating the exceptions table is as shown here:

CREATE TABLE original_table$EX  (
    [NDB$]server_id INT UNSIGNED,
    [NDB$]source_server_id INT UNSIGNED,
    [NDB$]source_epoch BIGINT UNSIGNED,
    [NDB$]count INT UNSIGNED,

    [NDB$OP_TYPE ENUM('WRITE_ROW','UPDATE_ROW', 'DELETE_ROW',
      'REFRESH_ROW', 'READ_ROW') NOT NULL,]
    [NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS',
      'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL,]
    [NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL,]

    original_table_pk_columns,

    [orig_table_column|orig_table_column$OLD|orig_table_column$NEW,]

    [additional_columns,]

    PRIMARY KEY([NDB$]server_id, [NDB$]source_server_id, [NDB$]source_epoch, [NDB$]count)
) ENGINE=NDB;

The first four columns are required. The names of the first four columns and the columns matching the original table's primary key columns are not critical; however, we suggest for reasons of clarity and consistency, that you use the names shown here for the server_id, source_server_id, source_epoch, and count columns, and that you use the same names as in the original table for the columns matching those in the original table's primary key.

If the exceptions table uses one or more of the optional columns NDB$OP_TYPE, NDB$CFT_CAUSE, or NDB$ORIG_TRANSID discussed later in this section, then each of the required columns must also be named using the prefix NDB$. If desired, you can use the NDB$ prefix to name the required columns even if you do not define any optional columns, but in this case, all four of the required columns must be named using the prefix.

Following these columns, the columns making up the original table's primary key should be copied in the order in which they are used to define the primary key of the original table. The data types for the columns duplicating the primary key columns of the original table should be the same as (or larger than) those of the original columns. A subset of the primary key columns may be used.

The exceptions table must use the NDB storage engine. (An example that uses NDB$OLD() with an exceptions table is shown later in this section.)

Additional columns may optionally be defined following the copied primary key columns, but not before any of them; any such extra columns cannot be NOT NULL. NDB Cluster supports three additional, predefined optional columns NDB$OP_TYPE, NDB$CFT_CAUSE, and NDB$ORIG_TRANSID, which are described in the next few paragraphs.

NDB$OP_TYPE: This column can be used to obtain the type of operation causing the conflict. If you use this column, define it as shown here:

NDB$OP_TYPE ENUM('WRITE_ROW', 'UPDATE_ROW', 'DELETE_ROW',
    'REFRESH_ROW', 'READ_ROW') NOT NULL

The WRITE_ROW, UPDATE_ROW, and DELETE_ROW operation types represent user-initiated operations. REFRESH_ROW operations are operations generated by conflict resolution in compensating transactions sent back to the originating cluster from the cluster that detected the conflict. READ_ROW operations are user-initiated read tracking operations defined with exclusive row locks.

NDB$CFT_CAUSE: You can define an optional column NDB$CFT_CAUSE which provides the cause of the registered conflict. This column, if used, is defined as shown here:

NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS',
    'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL

ROW_DOES_NOT_EXIST can be reported as the cause for UPDATE_ROW and WRITE_ROW operations; ROW_ALREADY_EXISTS can be reported for WRITE_ROW events. DATA_IN_CONFLICT is reported when a row-based conflict function detects a conflict; TRANS_IN_CONFLICT is reported when a transactional conflict function rejects all of the operations belonging to a complete transaction.

NDB$ORIG_TRANSID: The NDB$ORIG_TRANSID column, if used, contains the ID of the originating transaction. This column should be defined as follows:

NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL

NDB$ORIG_TRANSID is a 64-bit value generated by NDB. This value can be used to correlate multiple exceptions table entries belonging to the same conflicting transaction from the same or different exceptions tables.

Additional reference columns which are not part of the original table's primary key can be named colname$OLD or colname$NEW. colname$OLD references old values in update and delete operations—that is, operations containing DELETE_ROW events. colname$NEW can be used to reference new values in insert and update operations—in other words, operations using WRITE_ROW events, UPDATE_ROW events, or both types of events. Where a conflicting operation does not supply a value for a given reference column that is not a primary key, the exceptions table row contains either NULL, or a defined default value for that column.

Important

The mysql.ndb_replication table is read when a data table is set up for replication, so the row corresponding to a table to be replicated must be inserted into mysql.ndb_replication before the table to be replicated is created.

Examples

The following examples assume that you have already a working NDB Cluster replication setup, as described in Section 23.6.5, “Preparing the NDB Cluster for Replication”, and Section 23.6.6, “Starting NDB Cluster Replication (Single Replication Channel)”.

NDB$MAX() example.  Suppose you wish to enable greatest timestamp wins conflict resolution on table test.t1, using column mycol as the timestamp. This can be done using the following steps:

  1. Make sure that you have started the source mysqld with --ndb-log-update-as-write=OFF.

  2. On the source, perform this INSERT statement:

    INSERT INTO mysql.ndb_replication
        VALUES ('test', 't1', 0, NULL, 'NDB$MAX(mycol)');
    

    Inserting a 0 into the server_id indicates that all SQL nodes accessing this table should use conflict resolution. If you want to use conflict resolution on a specific mysqld only, use the actual server ID.

    Inserting NULL into the binlog_type column has the same effect as inserting 0 (NBT_DEFAULT); the server default is used.

  3. Create the test.t1 table:

    CREATE TABLE test.t1 (
        columns
        mycol INT UNSIGNED,
        columns
    ) ENGINE=NDB;
    

    Now, when updates are performed on this table, conflict resolution is applied, and the version of the row having the greatest value for mycol is written to the replica.

Note

Other binlog_type options—such as NBT_UPDATED_ONLY_USE_UPDATE should be used to control logging on the source using the ndb_replication table rather than by using command-line options.

NDB$OLD() example.  Suppose an NDB table such as the one defined here is being replicated, and you wish to enable same timestamp wins conflict resolution for updates to this table:

CREATE TABLE test.t2  (
    a INT UNSIGNED NOT NULL,
    b CHAR(25) NOT NULL,
    columns,
    mycol INT UNSIGNED NOT NULL,
    columns,
    PRIMARY KEY pk (a, b)
)   ENGINE=NDB;

The following steps are required, in the order shown:

  1. First—and prior to creating test.t2—you must insert a row into the mysql.ndb_replication table, as shown here:

    INSERT INTO mysql.ndb_replication
        VALUES ('test', 't2', 0, NULL, 'NDB$OLD(mycol)');
    

    Possible values for the binlog_type column are shown earlier in this section. The value 'NDB$OLD(mycol)' should be inserted into the conflict_fn column.

  2. Create an appropriate exceptions table for test.t2. The table creation statement shown here includes all required columns; any additional columns must be declared following these columns, and before the definition of the table's primary key.

    CREATE TABLE test.t2$EX  (
        server_id INT UNSIGNED,
        source_server_id INT UNSIGNED,
        source_epoch BIGINT UNSIGNED,
        count INT UNSIGNED,
        a INT UNSIGNED NOT NULL,
        b CHAR(25) NOT NULL,
    
        [additional_columns,]
    
        PRIMARY KEY(server_id, source_server_id, source_epoch, count)
    )   ENGINE=NDB;
    

    We can include additional columns for information about the type, cause, and originating transaction ID for a given conflict. We are also not required to supply matching columns for all primary key columns in the original table. This means you can create the exceptions table like this:

    CREATE TABLE test.t2$EX  (
        NDB$server_id INT UNSIGNED,
        NDB$source_server_id INT UNSIGNED,
        NDB$source_epoch BIGINT UNSIGNED,
        NDB$count INT UNSIGNED,
        a INT UNSIGNED NOT NULL,
    
        NDB$OP_TYPE ENUM('WRITE_ROW','UPDATE_ROW', 'DELETE_ROW',
          'REFRESH_ROW', 'READ_ROW') NOT NULL,
        NDB$CFT_CAUSE ENUM('ROW_DOES_NOT_EXIST', 'ROW_ALREADY_EXISTS',
          'DATA_IN_CONFLICT', 'TRANS_IN_CONFLICT') NOT NULL,
        NDB$ORIG_TRANSID BIGINT UNSIGNED NOT NULL,
    
        [additional_columns,]
    
        PRIMARY KEY(NDB$server_id, NDB$source_server_id, NDB$source_epoch, NDB$count)
    )   ENGINE=NDB;
    
    Note

    The NDB$ prefix is required for the four required columns since we included at least one of the columns NDB$OP_TYPE, NDB$CFT_CAUSE, or NDB$ORIG_TRANSID in the table definition.

  3. Create the table test.t2 as shown previously.

These steps must be followed for every table for which you wish to perform conflict resolution using NDB$OLD(). For each such table, there must be a corresponding row in mysql.ndb_replication, and there must be an exceptions table in the same database as the table being replicated.

Read conflict detection and resolution.  NDB Cluster also supports tracking of read operations, which makes it possible in circular replication setups to manage conflicts between reads of a given row in one cluster and updates or deletes of the same row in another. This example uses employee and department tables to model a scenario in which an employee is moved from one department to another on the source cluster (which we refer to hereafter as cluster A) while the replica cluster (hereafter B) updates the employee count of the employee's former department in an interleaved transaction.

The data tables have been created using the following SQL statements:

# Employee table
CREATE TABLE employee (
    id INT PRIMARY KEY,
    name VARCHAR(2000),
    dept INT NOT NULL
)   ENGINE=NDB;

# Department table
CREATE TABLE department (
    id INT PRIMARY KEY,
    name VARCHAR(2000),
    members INT
)   ENGINE=NDB;

The contents of the two tables include the rows shown in the (partial) output of the following SELECT statements:

mysql> SELECT id, name, dept FROM employee;
+---------------+------+
| id   | name   | dept |
+------+--------+------+
...
| 998  |  Mike  | 3    |
| 999  |  Joe   | 3    |
| 1000 |  Mary  | 3    |
...
+------+--------+------+

mysql> SELECT id, name, members FROM department;
+-----+-------------+---------+
| id  | name        | members |
+-----+-------------+---------+
...
| 3   | Old project | 24      |
...
+-----+-------------+---------+

We assume that we are already using an exceptions table that includes the four required columns (and these are used for this table's primary key), the optional columns for operation type and cause, and the original table's primary key column, created using the SQL statement shown here:

CREATE TABLE employee$EX  (
    NDB$server_id INT UNSIGNED,
    NDB$source_server_id INT UNSIGNED,
    NDB$source_epoch BIGINT UNSIGNED,
    NDB$count INT UNSIGNED,

    NDB$OP_TYPE ENUM( 'WRITE_ROW','UPDATE_ROW', 'DELETE_ROW',
                      'REFRESH_ROW','READ_ROW') NOT NULL,
    NDB$CFT_CAUSE ENUM( 'ROW_DOES_NOT_EXIST',
                        'ROW_ALREADY_EXISTS',
                        'DATA_IN_CONFLICT',
                        'TRANS_IN_CONFLICT') NOT NULL,

    id INT NOT NULL,

    PRIMARY KEY(NDB$server_id, NDB$source_server_id, NDB$source_epoch, NDB$count)
)   ENGINE=NDB;

Suppose there occur the two simultaneous transactions on the two clusters. On cluster A, we create a new department, then move employee number 999 into that department, using the following SQL statements:

BEGIN;
  INSERT INTO department VALUES (4, "New project", 1);
  UPDATE employee SET dept = 4 WHERE id = 999;
COMMIT;

At the same time, on cluster B, another transaction reads from employee, as shown here:

BEGIN;
  SELECT name FROM employee WHERE id = 999;
  UPDATE department SET members = members - 1  WHERE id = 3;
commit;

The conflicting transactions are not normally detected by the conflict resolution mechanism, since the conflict is between a read (SELECT) and an update operation. You can circumvent this issue by executing SET ndb_log_exclusive_reads = 1 on the replica cluster. Acquiring exclusive read locks in this way causes any rows read on the source to be flagged as needing conflict resolution on the replica cluster. If we enable exclusive reads in this way prior to the logging of these transactions, the read on cluster B is tracked and sent to cluster A for resolution; the conflict on the employee row is subsequently detected and the transaction on cluster B is aborted.

The conflict is registered in the exceptions table (on cluster A) as a READ_ROW operation (see Conflict resolution exceptions table, for a description of operation types), as shown here:

mysql> SELECT id, NDB$OP_TYPE, NDB$CFT_CAUSE FROM employee$EX;
+-------+-------------+-------------------+
| id    | NDB$OP_TYPE | NDB$CFT_CAUSE     |
+-------+-------------+-------------------+
...
| 999   | READ_ROW    | TRANS_IN_CONFLICT |
+-------+-------------+-------------------+

Any existing rows found in the read operation are flagged. This means that multiple rows resulting from the same conflict may be logged in the exception table, as shown by examining the effects a conflict between an update on cluster A and a read of multiple rows on cluster B from the same table in simultaneous transactions. The transaction executed on cluster A is shown here:

BEGIN;
  INSERT INTO department VALUES (4, "New project", 0);
  UPDATE employee SET dept = 4 WHERE dept = 3;
  SELECT COUNT(*) INTO @count FROM employee WHERE dept = 4;
  UPDATE department SET members = @count WHERE id = 4;
COMMIT;

Concurrently a transaction containing the statements shown here runs on cluster B:

SET ndb_log_exclusive_reads = 1;  # Must be set if not already enabled
...
BEGIN;
  SELECT COUNT(*) INTO @count FROM employee WHERE dept = 3 FOR UPDATE;
  UPDATE department SET members = @count WHERE id = 3;
COMMIT;

In this case, all three rows matching the WHERE condition in the second transaction's SELECT are read, and are thus flagged in the exceptions table, as shown here:

mysql> SELECT id, NDB$OP_TYPE, NDB$CFT_CAUSE FROM employee$EX;
+-------+-------------+-------------------+
| id    | NDB$OP_TYPE | NDB$CFT_CAUSE     |
+-------+-------------+-------------------+
...
| 998   | READ_ROW    | TRANS_IN_CONFLICT |
| 999   | READ_ROW    | TRANS_IN_CONFLICT |
| 1000  | READ_ROW    | TRANS_IN_CONFLICT |
...
+-------+-------------+-------------------+

Read tracking is performed on the basis of existing rows only. A read based on a given condition track conflicts only of any rows that are found and not of any rows that are inserted in an interleaved transaction. This is similar to how exclusive row locking is performed in a single instance of NDB Cluster.

23.7 NDB Cluster Release Notes

Changes in NDB Cluster releases are documented separately from this reference manual; you can find release notes for the changes in each NDB Cluster 8.0 release at NDB 8.0 Release Notes.

You can obtain release notes for older versions of NDB Cluster from NDB Cluster Release Notes.